Change has come gradually in the last few years to Cleveland Park's two-block commercial district on Connecticut Avenue, bringing a new tone to the neighborhood without destroying its long-established character.

Along the strip between Macomb and Porter streets NW the red brick stores are vintage Main Street. There is a Depression-era post office, a public library, and a fire station built in 1916. The Uptown Theatre, the dowager of deco, looms in their midst; ethnic America has made its mark on the avenue in restaurants featuring Japanese, French, Irish, Chinese and Italian cuisine.

But the conversion of many of the surrounding apartments to condominiums in recent years and the opening of the Metro station at Connecticut Avenue and Ordway Street in December 1981 have brought in younger residents and customers, displacing some of the area's many elderly persons. New businesses have sprung up to cater to a more affluent clientele.

"It's the last of the really nice neighborhoods," said Seymour Weinstein, 59, looking out the window of his shop, the Cleveland Park Valet. "It's friendly and warm. The person who lives in this neighborhood never has to go anywhere else."

Among other changes, "crime has definitely increased," Weinstein said. "We're getting a younger crowd of professionals in a neighborhood that has had a lot of elderly. We've lost a lot of faces in the last 10 years."

As he spoke, a bus clattered past on the L route, known among some drivers as the "wood line" because of the number of riders who are dependent on canes and walkers.

"This is really two neighborhoods: the elderly are here during the day and the subway disgorges the young professionals in the evening," said Betty Taylor, 43, manager of Stein's Capezio, which stocks tights, leotards and shoes for dancers as well as costumes, masks, rhinestones and sequins.

In addition to Stein's, a ceiling fan store, a vintage clothing store, an exclusive women's boutique, an exercise studio, a bookshop and several restaurants have opened in recent years--and in some cases, quickly closed. They sit side-by-side with establishments that have been on the avenue 20 to 50 years. Like Cleveland Park's residents, they exist in an uneasy alliance of old and young.

The neighborhood's elderly tend to patronize the older establishments: the Roma Restaurant, the Safeway, the Peoples Drug Store, the Tropea Barber Shop and Weinstein's Cleveland Park Valet. Many meet daily for coffee at the Peoples' lunch counter.

The four women who work behind the counter are like family to many of their customers and often exchange gifts with them at Christmas time. Collectively, Chris DeLoatch, Corinne Funchess, Margie Sims and Mae Powell have 70 years of experience behind the counter. Their tenure is typical of many who work in the older Cleveland Park businesses.

Seymour Weinstein vows he will leave his dry cleaners "feet first." Wally Valentini, assistant manager of the Safeway for 21 years, said when he retires it will be from that store, even though he now commutes 35 miles to and from Damascus to work. Similarly, the Abbo family has run the Roma Restaurant for 53 years and the Tropea Barber shop is 55 years old.

"Whenever I walk in the door to the Roma, the same people are here. The same people!" said Bobby Abbo, 38, son of original owner Frank Abbo. "We've had one waitress here for 35 years and every day she waits on the same people. After you see someone for a long time, they're not elderly, they're just people."

The Roma is still decorated with stuffed lions, tigers and polar bears--trophies of the big-game hunts the late Frank Abbo took up after he was in his seventies, traveling to Africa, India and the North Pole. "Nothing is new here," said his son. "Everything is old. If I change one little thing, everyone says they liked it better the other way."

"Cleveland Park is waiting to be discovered," said Abbo, who is skeptical about the new places, wondering, "How many will be here in five years?"

Having outlasted two competitors, a small Safeway is the area's only food store. Younger residents jokingly call it the "Soviet Safeway" because of its limited selection and long lines. Older residents say they are more satisfied with the store, especially its personal service.

Assistant manager Wally Valentini knows many of his customers by name and takes as much interest in an older person with a walker as in the senators and congressmen. Two years ago, when he had to cancel his family's planned vacation trip to Italy for financial reasons, his customers secretly organized a fund-raising campaign and sent the Valentinis to Italy.

Next door to the Safeway, down a worn flight of stairs, Jack Dugan, a burly man of 40, manages the neighborhood's newest bar, The Club Soda, where customers dance to the rock and roll of the '50s and '60s.

Many newer residents say they are pleased with the subtle changes in Cleveland Park. On weekends, when younger people predominate in the shopping area, business is brisk in the antique shop, the Swensen's ice cream store and the Va-Ce, an Italian delicatessen.

Ann Greer, an editor for the Cultural Alliance of Greater Washington, summed up the feelings of many: "Cleveland Park is getting to be an uptown Georgetown."

Among those less pleased is Tilford Dudley, who moved to Cleveland Park with his family shortly before Pearl Harbor. He recalls a quieter commercial district that had "a good filling station with a pit for repairs, an excellent hardware store where they not only sold you the tools to fix things but showed you how to fix them, a large Giant supermarket, and the Rose Brothers store which bought, sold and repaired antiques."

Dudley, a retired attorney, was one of the residents who successfully fought for two years to block intensive residential development of Tregaron, a large estate on Macomb Street nearby.

Patricia Walmsley, vice chairman of Advisory Neighborhood Commission 3C and chairman of its planning and zoning committee, said the temporary victory at Tregaron has made developers wary of speculation in Cleveland Park.

Developers, she said, "ask themselves, 'Am I going to have to go through a similar battle ?' Every time something happens in Cleveland Park there's a big fight. There are a lot of attorneys in the area and developers aren't dealing with amateurs."

Walmsley said she keeps a watchful eye on requests for zoning changes that indicate development may be imminent.

Joe Jeff Goldblatt, 30, a Cleveland Park resident who owns the Wonder Company, an entertainment production business, said he is optimistic about the future of the Cleveland Park business district.

"It's changed," Goldblatt said, "but so has the neighborhood. If you're elderly and the least bit ambulatory, Cleveland Park offers everything. And yet it also offers items for the upscale market."

Until a few years ago, the offices now occupied by the Wonder Company housed a custom corset shop. "Across the hall was a small church and down the hall was a music teacher, Mrs. Ying-Ling, who took piano students," said Goldblatt.

The days of Mrs. Ying-Ling, the corset maker and the Rose Brothers are gone, but Cleveland Park still retains the personal touch for customers who seek it.

Mary Selles, 40, who runs Amaryllis, a small vintage clothing store that opened recently, said she appreciates "the flavor of this neighborhood. I don't want to be caught in the crosscurrents of Adams-Morgan and I can't afford Georgetown or Dupont Circle," she said. Her clientele, Selles said, is "largely young professional women and men who don't want to look like carbon copies. These are not costumes, but wearable classic clothing."

When a couple who appeared to be in their fifties entered the shop, the man reminisced to Selles about her predecessor in that location. The Woodley Market, a mom-and-pop grocery store that closed last year, "was a first-class food store," he said. "The elderly depended on them because they delivered. They are sorely missed. And the people there were so nice."

"We're nice too," said Selles, somewhat defensively. "Give us a chance."