Ms. Mary was emphatic: "If you want a great getaway weekend, the place to go is Wilmington, as in Delaware."

"Wilmington," I said tentatively. "As in, 'Heh, heh'?"

" 'Heh, heh,' hell," Ms. Mary said. "It is one great town, and it's only a two-hour drive from Washington. It's small enough to be friendly and big enough to be interesting, it has one of the best hotels in the country, and it isn't far from anywhere. Try it, you'll like it."

My wife and I did and we did. We came back full of good food and good memories and planning to go back soon, since one weekend barely suffices to scratch the surface.

Although it was founded by the Dutch in 1638, the City of Wilmington is officially only 150 years old, having found city status necessary in 1832 because of the booming -- sometimes literally booming -- business being done at the powder mills of Eleuthere Irenee du Pont de Nemours, a French royalist who fled the Revolution ours inspired. Until then the village had been a borough known as "Willingtown." Many of the city's historic buildings have been preserved and vast tracts of the surrounding countryside retain their Colonial or early-industrial character, largely because du Pont's descendants have been rich, acquisitive and desirous of being remembered as nice folks.

With a population of 70,000 -- down from a peak of 112,000, but urban-renewing and rising again -- Wilmington is barely two-thirds the size of Alexandria, yet supports two good new downtown hotels and one great old one: the HOTEL DU PONT on Rodney Square, built in 1913.

The du Pont, like the Hotel Roanoke, is a storied establishment that has managed to modernize without losing its tradition and spirit. It is quiet and dignified but far from stuffy; coat and tie are not required or even suggested, but it is such a beautiful setting that one cheerfully dresses up and tones down so as not to introduce a sour note, as when calling on a favorite and formal aunt.

The 280 rooms and suites are immaculate and range from very nice to luxurious; there used to be about twice as many, but most have been remodeled so that two small rooms have become one larger one. And they're beautifully furnished with the real stuff: If there was a square inch of Formica in the place we missed it. Our room was full of little touches such as shampoo, showercaps and complexion soap in the bathroom, sewing kits in the drawer with the shoehorn and the Gideon Bible, and complimentary chocolates left beside the turned-down bed.

But the essence of the du Pont is in the staff and service. They ask when you want your "complimentary coffee" (which is really a Continental breakfast) in the morning and it arrives five minutes early. If you call room service for seconds, don't try to sneak in a shower, because if they say it'll be there in 20 minutes, it probably will arrive in 10. Ask a charwoman if you can take a peek at the Gold Ballroom and she lays aside her mop, flings open the doors, turns on the lights and shares your delight in the Italian Renaissance "sgraffito" walls and fabulously ornate gold- coffered ceiling. Ask the doorman for directions to the New Castle historic district and he urges you to visit his mother: "Her house was built in 1700; she's just finished restoring it, and she'd love to show you around."

It was such service as we hadn't experienced since a budget-breaking visit to The Homestead, yet the bill was less than we have paid at crummy resort motels: $59.50 a night plus $5 a day for garage service (which includes a cheerful young man bringing the car to the door as often as you like). The rate is by the room, not the person, so you pay no penalty for kids; suites can be had for $10 extra, with various combinations of beds and no charge for cots.

There are several weekend package deals, with combinations of tours, theaters (there's one in the hotel) or car rentals, some of them including a $50 credit against dinner in the hotel's GREEN ROOM, one of the town's poshest restaurants. The huge SUNDAY BRUNCH (10 to 2) in the Green Room is de rigueur, since le tout Wilmington shows up after church. For $15 you get to stuff yourself shamelessly under genuine gold chandeliers while rubbing elbows with du Ponts, duPonts, DuPonts, Duponts and also-rans.

The dinner credit also may be used in the hotel's BRANDYWINE ROOM, which boasts a notable collection of Wyeth paintings and will reopen in October after remodeling. If you don't spend it all -- we bet you will -- the balance is returned. The rates, which apply Friday through Sunday nights, will hold through the end of the year. Get a couple of couples together and the hotel usually will be able to put you up in rooms with a common parlor at no extra charge.

Both the SHERATON-BRANDYWINE INN and the brand-new RADISSON WILMINGTON HOTEL have similar weekend offerings at even lower rates, and there are any number of tour packages. The Greater Wilmington Convention and Visitors Bureau keeps track of it all, and couldn't be more helpful.

There are so many places to go in the Brandywine Valley area that planning is necessary if you are the sort of person who likes to "do" a region thoroughly. We are slapdash tourists; this is how our visit went, as we followed the recommendations of Ms. Mary (who is a Wilmington native and chauvinist), the visitors bureau, hotel employees and several friendly people we met in the street: FRIDAY AFTERNOON commenced with a stroll through RODNEY SQUARE, where there is always something going on -- today it was an organized jump-rope contest -- and down MARKET STREET, which has been closed to traffic and redeveloped into a tree-shaded pedestrian delight. The people move at a leisurely pace more suggestive of North Carolina's Wilmington than of a mid-Atlantic commercial center. This is a working street, with hardly a boutique to be seen; most of the stores and restaurants were there already, some of them since before the turn of the century. We lunched well and cheaply at a sidewalk table at TARABICOS, est. 1906; with the bill came our first happy reminder that Delaware imposes neither sales nor restaurant taxes. Tarabicos will undertake to serve a nine-course dinner for $7.25, and we plan to go back and take them up on it.

While we ate we also feasted our eyes on the gorgeous cast-iron facade of the GRAND OPERA HOUSE across Market Street. It was built in Second Empire style in 1871 and nearly fell to the wrecker's ball on its hundredth birthday, but was rescued, restored and reopened in 1976. Its interior is even more captivating and "the acoustics are splendid," according to Bill the guard, who gave us an informal tour. We've made midwinter reservations already, and none too soon.

After showing us the statue of Rear Admiral Samuel Francis Du Pont, removed to a Wilmington park from its rightful and original place on Dupont Circle (please do not call or write about the various spellings of that name hereinabove and hereinafter), Ms. Mary drove us around the neighborhoods where some of the semi-rich folks live, and where she didn't grow up. Then she had us pause in silence for a moment in front of what everybody used to call the MILLDEW ROOM, a great old bar beside the babbling Brandywine that was run by a late, great old lady named Mrs. Hagee. "If you had come to Wilmington when I told you to, you wouldn't have missed her," she said.

We bowed our heads. Ms. Mary seized the spiritual moment to run us by the studio of sculptor CHARLES PARKS (you'd never find it, but when in Wilmington you can get directions by calling 654-0651), which is dominated by his four-story, stainless-steel ''Our Lady of Santa Clara," a study for a 90-foot version destined for the California city of that name. The work should give heart to those who fear for the future of Catholicism.

Ms. Mary had intended to take us to STANLEY'S, "where they make the best roast sandwich in North America," but the word was that the Pagans Motorcycle Club had roared up from Washington to get a mess of them, so she fell back to the JACKSON INN, a neighborhood tavern at the corner of Lancaster and Du Pont that has only recently recovered its equilibrium after having been awarded a star by Otto Dekom, the Wilmington restaurant guru. Otto liked the spiced shrimp, and so did we. The sun was setting as we arrived at BRANDYWINE RACEWAY (clubhouse admission $4) to invest in the trotters. The horses ran true to form, which is to say unpredictably, as did the clubhouse food, which is to say ample, undistinguished and expensive. But it is a great pleasure to occasionally throw money away at a racetrack, and the evening once again proved the infallibility of my system: Place show bets on the No. 1 horse in the first race, the No. 2 horse in the second race, and so on. If I had stuck to it, I would have broken even. I never stick to it, and I never break even. SATURDAY MORNING we lolled around the hotel until 10 and then drove to BRANDYWINE RIVER MUSEUM, about 20 minutes from downtown Wilmington in Chadds Ford, Pennsylvania, and devoted almost entirely to Wyeths, that remarkable painting family whose talent seems to concentrate rather than dilute through the generations.

Having overstudied the paintings, one may conveniently refresh the eye by periodically turning to the windows overlooking the river whereon families, fraternities and lovers engage in the placid pastime of TUBING THE BRANDYWINE.

Happily it appears to be the local ethic to bring along an extra tube to float a trash receptacle, so that the Brandywine flows unvexed by beer cans to HAGLEY MUSEUM (admission $2.50), site of the original du Pont's original black- powder mills and mansion. Noblesse oblige seems to have led the French aristocrat to build his house close enough to the factory to share the danger, so when the plant blew up, as it did from time to time, it didn't just rattle milady's teacups, it blew them out the window, sash and all. Nevertheless, both family and factory multiplied, to the point where most of the du Ponts have stopped attaching their name to their good works, pour encourager les autres.

Mrs. Hawk, our volunteer guide, led a tour that didn't seem canned nor pressed by a schedule, and we were sorry we couldn't spend more time strolling the 220 acres and chatting with the men who run the restored steam engine and the machine shop. Next time we'll block out half a day, and pack along a picnic lunch.

We were mighty thirsty by the time we got back to town, but ROSE'S WATER ICE at 1207 North Lincoln took care of that in short order. Rose's is run by Rose Trotto, who sells nothing but your genuine Italian lemon water ices with the peel in (plus, by popular demand, lemon-lime and cherry); no cigarettes, no candy bars, no square Nabs, no gum, no nothing but Italian water ice "made the way it always was, lemonade in an old-time machine like an ice-cream freezer, packed around with ice and rock salt and cranked till it freezes with these real tiny little crystals." It took Mrs. Trotto quite a while to spell this out because she was constantly serving the parched Wilmingtonians who stepped up to the window. "I'm not saying the ones they make in these Slurpee machines aren't good," she said, "I'm just saying we make it the way we were taught here on The Hill, this part of town you would call Little Italy. There's just three of us still doing it this way, JOHN'S at 5th and Lincoln and FUSCA'S on Union Street."

Long life, good health and wealth to Mrs. Trotto and John and Fusca, for the water ices revived us sufficiently to hike down Main Street in search of Wilmington's best Italian submarine sandwich. Ms. Mary had told us the name of the place, but we forgot, and Mrs. Trotto said maybe the laurel really belongs to CONSTANTINO'S, out in Claymont, and the fellow we asked on the street said, "Hey, there's two places here in the same block and they both make great subs, STEVE'S and I forget the other one."

Well, the neighborhood didn't look too promising, and neither did OLYMPIC SUBS & STEAKS at 205 West 7th, where we fetched up, but oh my dear the sub that Mike the man behind the counter built for $5 was everything a body could ask. It also was more than the two of us could eat, even when washed along by several of the cold cans of GENESEE CREAM ALE we took back to the hotel.

Nothing but a nap was possible after such a pigout, whereby we almost missed the light and water show at LONGWOOD GARDENS (admission $4), 12 miles from town. All the seats on the terrace were taken, so it was our accidental good fortune to discover that we could wander at will among the vast array of towering fountains during the half-hour show, which is gently orchestrated and admirably understated. The fountain shows start at 9:15 p.m. on Tuesdays and Saturdays from June through August only, but Longwood is open from 10 till dark and worth seeing every day of the year. There are four acres of plants under glass in the conservatory and nearly every specimen is superb; the senses reel. It's another du Pont extravaganza, of course, but you'll have to search hard to find the plaque that tells which member of the family built this one and left it to the public.

Longwood was supposed to close at 10:30, but we lingered and no one objected, and so it was 11:30 by the time we made our way back to town and the COLUMBUS INN on Pennsylvania Avenue, where service from the full menu was available in spite of the hour, although only in a rather noisy cocktail lounge that is one of Wilmington's favorite late-evening topping-off spots. Good shrimp piccante and fine rack of lamb, with wine and beer, came to $45 with tip; a comparable meal would have been something like $70 in Washington, if you could get it at midnight. And so to bed. SUNDAY MORNING we were up betimes and I went out in search of a Sunday paper. Oddly, none was available in the lobby -- the only lapse of which we could accuse the Hotel du Pont throughout the weekend -- and all the vending machines in the business district seemed to be empty. At length I found a man striding along with a newspaper and asked him where he got it. "It's two blocks up, and one over that way," he began. "Then you . . . no, you'd probably get lost. I'll show you." Whereupon he reversed his course and led me four blocks to the newsstand, as though it were the duty of any Wilmingtonian to tend to strangers.

After licking up the room-service croissants and buns (baked fresh daily in the du Pont's own kitchens), we were off to the restored historic district of NEW CASTLE, which like everything else was only minutes away from downtown, but New Castle was closed. That is to say that everybody, including the doorman's mother, was properly at church. We happily wandered the charming old town, site of William Penn's first landing in the New World; it looks much like Old Georgetown might if its residents had less money and more taste.

On the way back to the du Pont for brunch we stopped at the Arco station, buying a quart of oil as an excuse to use the bathrooms; we were suffering from an overdose of the hotel's delicious coffee. But the men's room was out of order and someone had driven off with the key to the ladies'.

As we stood there, on one foot and then the other, a woman who ha pulled up to the gas pumps approached us. "My house is just down the block, and you're welcome to use our bathrooms," she said. "I've been traveling, and I know how it is."

Well, we've been traveling, and that's how Wilmington is. WILMINGTON WAYS

You can harldy go wrong if you simply make reservations at the HOTEL DU PONT (302/656-8121) and put yourself in the staff's capable hands. Or just wander around and stop at what seems interesting, for the Brandywine Valley has scores if not hundreds of worthwhile attractions.

If you want to be orderly about it, call or write the Greater Wilmington CONVENTION AND VISITORS BUREAU (302/652-4088; P.O. Box 111, Wilmington, Delaware 19899). They are such nice folks that when we called from the hotel late Friday afternoon and asked whether they'd be open long enough for us to get down there, a young woman said, "Oh, I'll run them up to you." And run the four blocks she must have, for she was in the lobby with a giant packet of brochures by the time I got off the elevator.