She was down and out on the Left Bank, a hungry American student in arrears on the hotel rent, when the concierge caught her in a grocery, spending her last centimes on crackers and sardines. Laurie Blavin, 21, assumed her next bed would be the sidewalk.

What happened next "astounded" her. The concierge inquired if she had enough money to eat, then reached into her purse and pressed 200 francs (about $30) on the UCLA sophomore who has spent the last two years doing odd jobs in France. "I'll add it to your bill," she said.

Some might call such kindness just plain old French hospitality, but the French have never enjoyed a reputation as America's good buddy, and tourists have carped for years at rude treatment from surly waiters who never smile for a tip because it's already compris. The last Americans to get hugged by the French were soldiers who sent Hitler packing, and cynics say they didn't really mean it.

But all that may be changing, if startling anecdotes of courtesy like Blavin's are to be believed as they wing across the Atlantic on the lips of confused Americans returning home with croissant withdrawal, a tummy full of truffles and a nouveau glow for the French. Mon Dieu! they are gasping. The French are actually trying to be nice to Americans.

"I've been well treated," says Charlie Mott, 21, a Princeton student trekking after Hemingway for his senior thesis. "The waiters aren't nearly as bad as I thought they'd be. It's just as hospitable as Italy or Spain."

Indeed, Blavin says she was also rescued at a caf,e she frequents near Notre Dame, fed free salad and eggs by friendly waiters after her money ran out. She's been trying to figure what it's all about ever since she was first exposed to this apparent virulent epidemic of niceness.

"The French have gotten nicer," reflected Robert Borne, 58, a Paris taxi driver. "We are not stupid. We don't want to bite the hand that feeds us. We need tourists. We need business."

Such considerations never seemed to alter French manners in the past. Arrogance masked a national inferiority complex. Salesclerks broke into English at the first grate of an American trying to consummate a transaction in fractured Franglais. (Nowadays, Americans say compliments, not glares, greet their efforts.) Hypocrisy abounded: the French guzzled American whiskey, paraded about in blue jeans, boogied to American rock, then berated tourists for Vietnam, ghetto riots, poverty, the bomb.

"There was a lot of resentment before when America was so rich and powerful," says Borne. "But now the Japanese and the Germans are on top. We have high unemployment and inflation and so do you. We're in the same boat. So, naturally, the French are more forgiving."

If a Frenchman harbored pro-American sentiment in the past, he kept silent. For him, a visit to one of the (now 14) McDonald's dotting this tourist-infested city had overtones of a clandestine foray to an opium den. Some purists once considered preference for Big Macs over quiche, grounds for divorce. No more.

Now the French wear the Stars and Stripes on their sleeves, especially in the rural outback beyond Paris where French good old boys treat Americans just like plain folks down South. (Of course, even the provincials, as the Parisians call their rednecked brethern, make a distinction between their behavior and that of their Paris cousins. "I hate the Parisians," said one liquor store in Arras, a rural factory town in northwest France. "I never go there unless I have to. They're not very nice.")

But even at a table in the smoke-filled Brasserie Lipp, the Duke Zeibert's of the Left Bank, a young French businessman was overheard loudly defending America to a gray- haired companion denouncing the United States in a vulgar growl.

"Oh, they're not so bad," soothed the pro- American. "They're very unique people."

"They only think of themselves," groused the anti-American. "How dare they order us not to sell pipes (for the Siberian pipeline) to the Russians? What about our unemployment? Americans are . . . selfish!"

"You have to remember," smiled the pro-American, "they are a very young country. They are bound to make mistakes. They are still growing up, like teen-agers." The American eavesdropper choked on his Evian.

Some praise Francois Mitterand's socialist government for a sort of nouveau benevolence reverberating through the masses, as they soak the rich and threaten to bulldoze Brigit Bardot's villa wall in St. Tropez to make the exclusive topless beach public. Some francophiles believe that as the French learn to treat their fellow countrymen with more kindness, Americans are bound to benefit.

"People in the shops -- the working class -- are more friendly," says Ted Joans, 54, a black American poet. "They're not trying to imitate the petit bourgeoisie any more. Under (ex-Presidents) DeGaulle, Pompidou and Giscard, every Frenchman was a walking flag, very nationalistic, pompous."

He theorizes that such arrogance was contagious; the masses imitated their rulers, showering American tourists with snooty fallout from a false pride that masked a feeling of impotence on the world scene. "If you have a country ruled by kings, you have a lot of little kings running around," said Joans.

Cynics say the answer is economics. In this divine (for Americans) summer of the falling franc, the French have gotten desperate. And treating Americans kindly shows just how desperate they have become, some say: a flashback of German Occupation Syndrome.

But lest Americans think France has gone touchy-feely for Americans, with locals volunteering to guide tourists around treacherous mine-fields of poodle droppings fouling the city, forget it. Not everyone has undergone pro-Yank reeducation, says a researcher in the Paris bureau of a U.S. newsweekly. She still swats insults like voracious Marseille mosquitoes, having been "treated like crap by the grotty little man in my apartment. And I'm sure it's because I'm an American."

After asking the saleswoman in one fashionable shop for the belt rack, she was told, "The sign for information is up front. Are you blind?"

"But she treated her French customers the same way," said the American. "Just as nasty."

Despite boutique politics, disenchanted French youth are embracing American culture as never before, seeking identity in James Dean and Bogart, penny loafers and prep. More than a dozen theaters in Paris showing undubbed Silver Screen classics are jammed with Bogart junkies memorizing corny lines to try out on American friends. "Everyone greets you with something trite like, 'Hey, honey,' " laughs Blavin.

Charlie Mott has played Professor Higgins to more than one French Eliza who wanted to practice her slang. And French pals strut about American bars like The Front Page begging advice from Americans on how to dress and act truly preppie.

Indeed, boutiques can hardly keep what Mott calls "the frog outfit" in stock: loafers like Weejuns (some stuffed with real U.S. pennies), button-up Levis, Brooks Brothers shirts, tweed jackets. A Polo by Ralph Lauren is truly in. A French-made LaCoste shirt might be worn, but only because Americans wear them.

One French woman was spotted crossing the ritzy Rue Faubourg St. Honore in the sweatshirt of the University of Georgia, whose mascot is the bulldog. A knowledgable American confronted her with the all-purpose Atlanta greeting: "How 'bout them Dawgs?"

She didn't get it.

"They're disenchanted with the old French culture," says Mott. "In England, the kids were searching for something in punk. In France, they're hunting for life's meaning in prep."

And part of being preppie (and all-American) is being genuine, sincere, friendly, nice. Especially to other preppies who tend to be -- who else? -- Americans. Often, it's impossible to distinguish French preppies from the real thing, so perfect is the disguise, right down to the International Herald Tribune under the arm. They even mistake one another for Americans, and start acting nice. They see it doesn't hurt and it spreads.

Americans can now even demand ketchup without a glare. At the popular Cafe D'Alsace on the Champs Elysees, manager Mario Dos plants kisses on the hands of American women who plop down for fresh oysters, bratworst, saurkraut and beer. He clicks his heels, aims to please. He doesn't blink over an American's complaint that the grilled sole is undercooked. He simply rushes it back to the kitchen, emerging with one well-done.

"The French like it the other way (less cooked)," he explains without a hint of hauteur. "Paul Bocuse says to cook it lightly to keep the flavor." But in this miraculous summer of 1982 in France, the customer is always right, even if he is wrong -- and an American.