WASHINGTON'S homegrown American Cafe chain rapidly expanded over the years, then was sold to a major conglomerate. Along the way, an American Cafe executive told me, people complained that the restaurants' quality had dropped.

Said John de Napoli, the new vice president of operations, "The food at American Cafe after Mark Caraluzzi {the original chef-partner} left has taken a bit of a dip." And the service had a lot of problems. Now he is trying to "bring back the old taste of American Cafe food." He is also trying to "get the service up to par here."

De Napoli came several months ago after eight different jobs as general manager of restaurants from Washington (Fedora Cafe, Phineas Prime Rib, Charley's Place, Casa Maria and the region's El Torito and Casa Maria group) to New Jersey, New York, Connecticut and Boston. All this by age 28.

He came knowing there were service problems, and said he's changed much of the dining room management. When I reported several complaints I'd had about American Cafes, de Napoli made no excuses, had already had a meeting about one problem and immediately proposed to send a memo to the restaurants to rectify another. Sounds like American can-do spirit at work. Even so, I'll believe it when I taste it.

WHAT'S UP, DOCS? --

It's the most unexpected match since Elizabeth Taylor and John Warner: The Hard Rock Cafe and the American Medical Association have a living arrangement. The rock-and-roll restaurant, which keeps people standing in line even in such jaded cities as Los Angeles and London, has leased about 15,000 feet of space in the old PEPCO building at 999 E Street NW, which the AMA owns. Even Hard Rock Cafe's advertising company couldn't resist calling this electric-company renovation a "highly charged dining environment." But it will take a while for the "U.S. Embassy of Rock" to get established, so don't get in line yet.

THE GREAT TASTEBUDS TEST --

How many Napa Valley wineries can you visit in one day? The answer is 55, if the day is October 28 and you invest in a $35 admission ticket rather than airfare and rental car. And you can even get a partial tax rebate. The event is called a Grand Tasting and Wine Exploratorium, sponsored by the Napa Valley Growers and Vintners to benefit Washington's National Building Museum.

This mass wine tasting -- they hope to attract 1600 people -- will be from 6 to 9 in the Grand Hall of the museum, which is on Judiciary Square. Representatives of the wineries will be available to discuss as well as pour their wines, Lansdowne Catering is providing hors d'oeuvres, and the exploratorium will display grape-growing tools, barrel and vine samples in order to explain wine producing in the Napa Valley. For tickets or information call the museum's special events office at 272-2487.