CAPE MAY, N.J., that gingerbread Valentine handed down to us from Victorian days, was fashionable long before the motorcar and will undoubtedly survive the difficulties of finding gasoline for it. You can get to Cape May and back from Washington on a tankful and, once you arrive, you'll discover that America's oldest seashore resort was built for walking.

And what a charmer it is! The old streets are lined with wooden houses decorated with carvings that bring to mind the top of a wedding cake. Double verandas hung with wisteria, wicker rockers in a row, American flags hanging from upstairs windows - this is another age enclosed for us with neat white picket fences. Walk the cracked slate sidewalks under the gas lamps of the historical section of the town, and tip your hat to the folks who preserved this by designating it a National Historic Landmark.

Back in 1800, Philadelphia society discovered the charms of cool Cape May, arriving first by stagecoach in a journey that took two days and later flocking there by steamboat. By 1850, Cape May's social season rivaled Saratoga's, and the rich were building summer "cottages" by the sea to enjoy bathing on what was then so wide a stretch of beach that Henry Ford raced his new-fangled invention on its sands. The coming of the railroad watered down the opulence by bringing less well-heeled excursionists, a fact deeply deplored by local businessmen.

The worry now is not who will come but will they come. The vacancy signs were up recently at most of the pretty little guest houses lining the side streets, and the Mainstay Inn - "Pleasant accomodations," says the sign - is well booked, but usually has a few cancellations. The Chalfonte Hotel, this year celebrating its 103rd season, was not full for July but reports "good reservations" for August. The ferry over from Delaware has raised its prices from $8 for car and driver to $9.25 to offset the drop in customers. The changemaker in the booth at the Penny Arcade by the beach mutters that if things don't pick up from the slow Memorial Day weekend, the town is in trouble.

Canadians, who once flocked to Cape May in such droves that signs at the ferry gate are in French as well as English, may find it difficult to motor down this summer, but Washingtonians can make it without worry even if they don't get gas at all en route. The round trip to Lewes and the ferry over the Bay is about 250 miles. And, if you travel on a day matching your "odd-even" license plates, you might get a tankful in Delaware, as I did recently in Bridgeville. Don't expect, however, special dispensation for out-of-state plates.

If you're still nervous and want information about current gas conditions, New Jersey has a gas hot line (800 - 492-4242) - but just try to get through. Cape May has its own hot line, but it's not toll free (609 - 465-2111). Rely on your friendly Washington service station and by-pass those long lines which during my Delaware visit extended into the rural countyside.

Where else can you get such a bargain trip back into time that starts with a mini-ocean voyage? The Lewes ferry, churning its way ponderously across the bay to Cape May, may smell like French fries inside the main enclosed deck, but climb the companionway to the top with the gulls and the life boats and, after a while, you'll wonder where the deck steward with the boullion is. Share your sandwich with the gulls, and read your book in the sun while down below your car is riding without spending a drop of precious fuel.

Bring your bathing suit to Cape May, but don't expect splendid, wide beaches. Erosion has eaten them away until, at high tide, the water is close to the concrete-and-rock sea wall that the town built to keep the ocean from the beach cottages during storms. But, psst! Here's a not-well-known fact. Take the car up the south end of the beach by the jetty where the sand widens perceptibly. This is the fisherman's beach, away from the boardwalk, the shops and the action, but it is far nicer for lounging, and the anglers don't mind sharing.

Forget the motels, if you wish, and book quarters in one of the little white guest houses where a double room can cost as little as $18 per night. If you want a hotel, the venerable Chalfonte is at Howard and Swell Streets. It's a beauty and one of the few buildings to survive the great fire of 1878. The old Colonial Hotel just off Beach Avenue is drawing many young people with families. This ancient, lovely pile put on Wallis Warfield's coming out party back in 1915, long before anyone had any idea she would change the line of English succession.

But the jewel of them all has got to be the Mainstay. If you're lucky enough to pick up a cancellation there, you're in for a treat. This elegant Victorian mansion is far and away the most interesting inn in this old resort, partially because of the personality of its new owners, Tom and Sue Carroll.

Tom Carroll was a Coast Guardsman doing a tour of duty at Cape May when he fell in love with the Victorian age. Today he seems actually to have moved back into it and he has created the complete antidote to today's cookie cutter motels. The Carrolls have lovingly restored this elegant example of the Italianate style which was built in 1872 as a gentlemen's gambling club. The Carrolls have done a sweet job, from making lace curtains for all 64 huge windows to choosing the music for the grand piano and the hats for the hatrack in the hall.

Upstairs, which you will not see unless you can book a room, is a copper bath tub framed in wood, marble-topped dressers, armoires, massive beds and chamber pots that roll out on trays from underneath. You can see these rooms, which go for between $26 and $35 per night, in pictures in a book in the lobby and envy the fortunate occupants who will also get a sumptuous breakfast served on the veranda in good weather and in the dining room under the beautiful chandelier if the weather is foul.

The Carrolls rather pretend the paying bed-and-breakfast guests are friends and give them the run of the place, from the living room to the cupola where the gamblers' lookout used to be posted. They do say tactfully, however, in their brochure that "young children generally find us tiresome." If you can't get a room there, come anyway for the tour on Saturdays, Sundays, Tuesdays and Thursdays at 4 p.m., when $2 will get you an amusing account of the history and restoration of Mainstay along with tea and homemade cookies on the veranda afterwards. This is a real charmer.

The Pink House is an antique shop that is a must for visitors, an elaborate confection that was, in 1879, the summer cottage of Eldridge Johnson, probably the same man who founded the Victor Talking Machine Co. John and Nancy Miller from Leesburg own it now and they say the Johnsons didn't use the house much because Mrs. Johnson thought Cape May was provincial. The Pink House is not far from Washington Mall's array of shops and is easy to spot because of its Valentine color and the ancient big-wheel bicycle on the front porch. The house appeared on the cover of the New Yorker a while back.

Do spend some precious fuel to vist the fishing wharf just outside the town limits, and have a meal at the Lobster House, where you can dine overlooking the bay and have a preliminary cocktail on a sloop tied to the dock. Stroll along the wharf afterwards, and watch the fishermen unload their salty catch destined for city tables. The moderate priced Jetty Restaurant at the end of Beach Drive is another place fish-lovers should visit. The bluefish that appear on the Jetty's plates were swimming in the ocean that morning.

Cape May restaurants often have an early dining hour - 4:30 to 6 p.m., when prices are lower than at the later hour - possibly to attract Cape May's large number of retired people. The Merion Inn, not far from the beach, is one that offers this bargain.

"Don't forget to speak scornfully of the Victorian Age," said J. M. Barrie, "there will be time for meekness when you try to better it." Fill the tank and run down and see if you agree. Cape May boasts the greatest concentration of mid-Victorian structures in the country, and you'll have a great opportunity to make up your mind.

Trade in city discos for a band concert on the green, walk the old streets lined with sweet-smelling ligustrum, take tea swinging in the veranda glider at the Mainstay.

You may not want to go back home. CAPTION: Picture 1, Cape May: The Pink House; Picure 2, and the commercial fishing pier, by Elizabeth C. Mooney for the Washington Post.; Picture 3, no caption, By Elizabeth C. Mooney for The Washington Post