The nuns would have been horrified. My best Friend, sitting on a park bench, soliciting companionship for the night, using the language of the gutter. But for Mercedes, it was the biggest break in her nine-year struggle to earn a decent wage. It was her movie debut as an actress, in the role of a police decoy in "The Warriors," which opened nationwide early in February. I saw the film on the day it opened. She didn't; she was busy . . . waiting on tables.

Mercedes Ruehl divides the world into two groups: those who make jokes about her first name and those who don't. "The latter," she says, "are in a distinct minority."

She has been may friend since the mid-1960s when we arrived, 17, full of hope, adored-and self-adoring-for our promise, at a small Catholic woman's college in New York. She had just graduated from Regina High School in Silver Spring, Md. The college had only one famous alumna-the acidulous columnist Dorothy Kilagallen-something we hoped to correct. However, ambition was discouraged in all sorts of ways; not the least being the old nun who ran the infirmary. She used to give out the same pills, no matter what the complaint, and in a quivering voice she would warn, "These are the pills that killed Dorothy."

Feshman year was 1965. Auxiliary troops were in Vietnam. The nation's ghettos were in Flames. A handsome president was in his grave, his successor a twanging Texan. We called the nuns "mother" and rose with the silence of sinners whenever they entered a classroom. The rules were stringent: soft-soled slipper were required in the dorms after 10 p.m.

Mercedes' room was down the hall from mine in Sst. Ursula's dorm. The day I arrived, she stared at my red Amelia Earhart luggage, which my mother had purchased with S&H green stamps. "If somebody gave me luggage names afte the most famous missing person in history," she said, aghast, "I would take it as a hint." I admired her forthrightness. We discovered we were both intent on experiencing men and the world, in either order, though at the time the two seemed synonymous. We became fast friends.

On Friday nights of that first year, we would assign ourselves to mixers at different schools: "You take Fairfield, I'll tackle Fordham." We were looking for what she called "the not-impossible he." Our requirements were tough: "He" could not be a "mathmajor," pronounced as one word, and must have a "friend." After the midnight curfew, we would get a soda and a candy bar for a quarter and sit in the smoker downstairs in the dorm, deciding whether or not we had found him, and then spending the next week taking turns as sentries of the pay phone, hoping "he" had a dime.

We stayed at this genteel school the obligatory four years, mastering, among other dying arts, the ability to pray in three languages.

I wanted to transfer after six weeks; but my mother, oblivious to the message of the luggage, said it would be "unethical," because I had a scholarship. Mercedes accepted her lot, or was able to see the romance in it: the dying order of schools like ours, schools that had tea dances and dinners that were served, curfews and compulsory spiritual retreats and rules like "no students may wear slacks on campus unless covered by a raincoat."

I sublimated my wanderlust by becoming editor of the school paper. She seized the day and became president of the theater club. I would write drama reviews, praising her alto. She would write letters to the editor, thanking the paper for stirring up concern on some major issue like whether or not the school should go coed (Headline: Are Female Ghettoes an Anachronism?). She was particularly effulgent about the paper's one effort at muckraking, the chance discovery that during the 1930s Benito Mussolini had donated some books to the college library. "He must have had a mistress here," she theorized, scandalizing the nuns.

After graduation, our bond was that of army buddies, of having done time in a place that chose us, more than we chose it. Because we both had complicated relationships with authority, neither of us earned particularly good grades.However, we were sure that once we entered the real world, we would get good jobs in our chosen fields, the rogue professions of jornalism and theater. We moved to New York, where I would attend journalism school and she would land a job in show business.

It was the summer of Woodstock, Nashville skyline, Charlie Manson. For us it was the summer of living in an apartment with cockroaches and subsisting on a daily menu heavy with hot dogs. Every evening the converstaion was the same. The one: "It's your tune to kill the bugs." The other: "Okay, you heat up the hot dogs." In unison: "You can cut the paths with a knife." The only person who seemed more naive and less citified than we was my 15-year-old brother, who visited one weekend and spent $7 at a subway boutique in Times Square on a souvenir billfold that said "genuine wallet." Although it was difficult, we tried to wear our sense of destiny like armor.

She stated out in show business with a 9-to-5 job scheduling commericals for ABC radio. For 10 weeks, one-third of her salary was to go to the agency that found her the job; she stayed at the job for 10 weeks. She has been on her own ever since, either working in theater or as a waitress. For nine years she has refused to succumb to the world's notion of success, to do what the amorphous majority suggest: submit to a life that is not mad with desire-the desire for greatness, stature, renown; the desire to practice her art. She is the only person I have ever met who literally invents each day as it happens.

She has managed, more or less, to ignore the people she calls the "megaphone men." She shoplifted that phrase from an observation once made by Eugene O'Neill, and observation she had written down and assessed and examined many times: "In this faith I live, that if I have the 'guts' to ignore the megaphone men and what goes with them, to follow the dream and live for that alone, then my real significance will be in trying, and the ability to express it will be conquered in time, not tomorrow or the next day nor any near-easily attained period, but after the struggle has been long enough and hard enough to merit victory."

I left the city after that one year. My first job was on a small newspaper in Connecticut; the executive editor told me that if I was really good, I might make it to Providence, R.I., in "three, five years." Mercedes stayed in the city. For a while, she got caught up in that spirit-sapping scene where, under some misguided interpretation of the artist's mandate to experience life to the fullest and out of desperate need to make some money, actors wait on tables or become bartenders. She finally stopped when, taking a cab home one dawn, she realized she felt "really old." She was almost 23. Now the waitressing jobs are strictly emergency measures in the face of the incontrovertible financial demands.

These days, I get to see her about once or twice a year when I am in the city on business. I stay in her studio apartment, the one she calls the world's smallest human dwelling, which is in the Chelsea section of Manhattan, just north of Greenwich Village, just south of Hell's Kitchen, on a tree-lined street. It has a warm, womb-like air, uncluttered despite the smallness, filled with delicate touches like the cut-glass unicorn on the sill of the louvered windows.The windows look out on an abandoned backyard wild with weeds, toward a row of empty buildings, up at an urban sky that sometimes surprises with its stars.

I saw her last January. We exchanged belated Christmas presents. For her, a yellow, silky blouse. For me, a box of madeleines, the French wafers that inspired Proust to memories of times past. Both of us recently turned 30.

Mercedes: "I have a certain faith that I'll still look young for a while, that the muscles will stay in place because I am still struggling, unsatisfied. I have not yet turned that little corner into complacency." I think to myself that she will continue to look yopung as long as she continues to think she has a control over it. I have always marveled at her sanguine side, a uniquely high regard she has for herself, an ongoing faith. I have no idea how it came about, though I have supposed it may come from two happy accidents of genetics: she is left-handed, and she is tall. People who are left-handed see the world as a conspiracy of northpaws and from nursery school on are fighting for the right to do things in their way. She is at least 5 feet, 10 inches-slim, dark-haired, with eyes that seem to study. It is an emphatic appearance that effortlessly calls attention to itself. It is as if she feels an obligation to the attention her height creates, to pay it back with her wits, to pay it back on stage.

The conversation turned to men: She is newly involved. "Are you in love?" I asked. She pondered the question. "Look, I know it's a slippery term, but do you feel really close to this guy?" The answer, considered, is yes, yes, she does.

Finally, careers. This time, she is wavering. A movie is opening soon, on Feb. 9, and she has what she calls "a smart part with loathsome lines in a film whose overall integrity I doubt."

"That's laying it on the line," was my response.

"And," she said, "I'm out of bucks. I may have to take a waitressing job. A couple of weeks ago, for the first time in my life, I lived on $5 a week." I know that was true because she had writeed to me then: "Poverty is a graceless and entirely unromantic state when it overstays its welcome, which it had done in my case for about six years."

Sometimes she thinks about leaving theater, leaving behind the daily phone calls to the megaphone men, the people who line up the auditions for shows and commercials, the guys who supply the work as extras. She knows some actors who would rather starve than do extra work. "I've tried starving," she says to explain her decision to be an extra on Woody Allen's new film, "Manhattan."

But what would you do?"

"Ah, there's the rub. I have never wanted to do anything but act. It has been there as an accepted fact, a standing dream, a lasting intention I have never really assessed or examined. I have lived with the dream of being an actress with a child's faith; it has been a non-negotiable fantasy."

In her best year as an actress, she earned about $10,000. That was a year ago, when she played in "Vanities" to excellent notices inCincinnati, Cleveland, Houston, Indianapolis. The same week she lived on $5, she was offered the chance to do "Vanities" again, this time in Philadelphis, for " $300 a week plus room." She said she could not do it; her passion for play had run out. "Life in the theater means regularly producing great passion eight times a week. It is hard to do truly, especially when it is always possible to do it technically, to fake it. If I had taken that job in Philly, I would have been faking it. Or at least running that risk.

"Maybe I should go into teachin," she said. "Get a master's degree and schmooze some college into hiring me. I sometimes hope I can do that. Well, I don't hope that will happen. It's just that every now and then I think I should do something a grwonup does, get a real job with a regular income and not live as a gypsy, do something respectable."

I cringed.

She smiled, "That's what I was hoping you'd say.

"Maybe the reason you haven't made it big yet is that you have a neurotic affection for poverty.

"I would not put anything past my subconscious, but I don't think that's it," she said, shaking her head.

"You never could have made it as an ingenue. You are too tall, too dark, too knowing."

She began to sound encouraged again: "I sometimes think I am just now coming into the time of my readiness."

She told a story about how she remembers once reading an interview with the actor Nicol Williamson, in which he said he did his best acting when contemplating his own death. "I was 21 the first time I read that and I remember thinking, 'How does one contemplate one's own death? Do you think of your coffin? Its color? Length?'"

Now she thinks she understands, she thinks it means it does not matter whether the audience catches an actor bleeding or dancing really bleeding, really dancing. The only thing that matters is that "you hold back nothing. Why hide? You might die at any time. Tomorrow or 40 years form now, the time will come when you cease to be, and in view of that irrefutable truth, why hold back anything? Why pretend you don't know what you do know? The time will come when you do not have the sweet joy of saying what must be said the way it should be said, so you may as well do it now with intensity and with . . ," she paused,". . .self-surrender."

By now a bottle of wine has been drunk. We have once again toasted our bond, still the bond of bright futures, not, at least not yet, the bond of lost promise.

On Feb. 9, thousand of miles apart, in separate cities, I went to see my friend in "The Warriors." It is a macho film, the story of a street gan in New York that must return 27 miles by subway and on foot from the Bronx to their own turf on Coney Island. The city's largest gangs met peacefully in the Bronx to consider banding toghether and taking over the city.But when the leader of the largest gang is killed, the truce is shattered and the Coney Island gang ("the Warriors") is accused of the murder. They have no weapons and face an endless assault by other gangs, including a posse of police made to seem like any other roving band of marauders.

I would have been happy if the Warriors had just hailed a cab and stopped all their underground nonsense early in the film, were it not for my desire to see my friend. After they had made their snare-filled way to Central Park from Bronx, and still no sight of Mercedes, I began to panic: had she been eited out? I revived the dead art of praying in three languages, beseeching Deus, Dieu , God, whoever, that she would appear.

Finally, it happened. A long, leisurely pan to a park bench, where sits a dark-haired woman in jeans and an orange blouse. I am all adrenalin. So is one of the Warriors who spots her and decides to pause in his dangerous retreat. His friends tell him to hold off, but he is stubborn. Too bad for him. I know what's going to happen.

Mercedes said she studied the script last summer when the filming took place and was somewhat appalled by the cheapness of the language, but against her better instincts (and probably in light of the $1,200 she would earn) decided to give it a try. An old acting coach once advised her to give any scene the highest stakes possible and her subtext for how to interpret the role of this decoy was that it is the girl's first time out as a decoy: "I would make her a little awkward, a little funny, very relieved and proud when she finally catches the guy."

Her director, Walter Hill, disagreed: "I want her cool as a prostitute."

The longest learned lesson in my acting career," says Mercedes, "is that if you want to do something one way and your director wants to do it another way, you have to come up with a third approach you can both live with."

The Warrior saunters over to my best friend, looking for all the world as if he means no good. This is obviously not a "not-impossible he" at a Fordham mixer. "You looking for some company?"

"Whatever you say," says the Warrior, trying to appear smooth.

"Why don't you sit down and keep me company?" Mercedes says, in what sounds like an abridgement of his constitutional right to commit a crime without being baited into it.

"Look at all those muscles," she says. "I bet the chicks like all those muscles. Why don't you show me what you do with the chicks?" So much for his constitutional rights: bold-faced entrapment.

He grabs her. They tussle.

"Hey, take it easy. Not so fast," says my friend, in what sounds to me like a brilliant alto-sinking, sultry, a voice that should be serving the poetry of a Hedda, a Blanche, a Masha.

"You don't understand, lady. I like it rough."

A major struggle; a strife of bodies. The camera to the rescue.By some miracle of trickery know only to the modern lens, my friend subdues her attacker. He is next seen handcuffed to the park bench.

She is suddenly shouting, "Your nights in the park are over. You're under arrest."

"C'mon lady," he says once again, this time yanking the park bench a distance of several feet. It looks as if he may break out of his shackles. She blows the whistle again.

"Please," he says, giving the bench a violent yank. There is a sound of sirens and the imminent arrival of a squad car.

"Kiss my ass," says Mercedes.

With that, her debut is done. I am inordinately proud of her, even though I disliked the movie and I did think her lines were rather coarse. At the risk of participating in the very vulgarity she despises, and so condoning it, here's to the day the megaphone men kiss hers. CAPTION: Picture 1, no caption; Picture 2, Mercedes Ruehl, top left, had a $1,200 bit part in the current movie "The Warriors."