Open Tuesday through Sunday, noon to midnight. No credit cards. Reservations. Price: Main dishes $3 to $3.50; Cafe Lovcen 2132 Florida Ave. NW. 462-2046. Open Monday through Saturday, 8 a.m. to 3 p.m., 6 p.m. to midnight; Sunday, 10 a.m. to 3 p.m. No credit cards. Reservations. Price: Dinner main dishes average $5 to $6; full dinners about $30 a couple with wine, tax and tip.; Serbian Crown 4529 Wisconsin Ave. NW. 966-6787. Open Monday through Friday, noon to 3:30 p.m.; daily, 6 to 11 p.m. AE, CB, D, MC,V. Reservations. Price: Dinner main dishes average $9 to $11; full dinners about $50 to $60 a couple with wine, tax and tip.; Bayon Market 940 Bonifant St., Silver Spring. 588-1546. Open daily, 10 a.m. to 11 p.m. No credit cards. No reservations. Price: Dishes average $2 to $3.

So worldly have we in Washington become that we hohum another new Szechuan restaurant and blink not an eye when a sixth Thai kitchen opens. We consider our two Afghan restaurants just a normal part of dining scene; only the novelty of a restaurant serving authentic American food would be guaranteed to quicken the pulse of the Washington diner.

But several other unfamiliar cuisines have been more or less recently added to the local menu. Here are the results of explorations into that territory.

In Ethopia, the thin, porous pancakes called injera are gray, fermented from a grain known as tef. In Washington's Ethopian restaurant, first in this country and maybe the first anywhere outside of Africa, the injera are white, like linen pancakes, having been made from wheat fermented six days in plastic buckets. In Ethiopia, the injera are cooked on an earthenware griddle ovver a eucalyptus fire; in Washington, they are cooked in an electric frying pan. But Mamma Desta is inventive, and has devised American substitutes - wheat for tef, sour cream for soft cheese called lab - to reproduce Ethiopian food, seasoned with red peppers known as berberi, has been called the hottest in Africa. Mamma Desta's food does not come close to being even the hottest food on Georgia Avenue.

What is authentic is the method of eating these pancakes and meats and pounded red pepper pastes. Leave your floppy sleeves and neckties for another day. Roll up your sleeves. You eat with your hands. The waiter brings a pizza pan draped with injera and a series of bowls filled with watts - thick stews of beef, chicken with a hard boiled egg, lamb or vegetables - and tibs - coursely chopped beef fried with onions and a little hot pepper - along with another plate of injera. You spoon mounds of each dish on the communal pizza pan, tear off pieces of pancake, and scoop up the food in it. No forks, no private property, plenty of napkins. Wash it down with beer (or, according to the menu, soda, milk, orange juice, instant coffee or tea, none of which sounds even vaguely Ethiopian). Swipe up a bit of berberi paste if you find the seasonings insufficient, a little sour cream if you like your pepper tamed. That's it, the whole meal - feast, rather. The entertainment you provide yourself, learning to cope with the technique. The waiter-manager comes by to give a short lesson, offers you second helping, promising all you can eat. He shows a review from a Baltimore newspaper.He talks of his plans to import Ethiopian baskets for serving and low stools for seating. Mamma Desta herself may change her white uniform and head draping for a Western red dress and make the rounds of the tables. Washington's Ethiopian community drifts in and out and around. Through it all you tear and dip and bite, getting the hang of it, the faintly exotic spices growing on you. All this under Chinese lanterns from the restaurant's previous incarnation, in a room that tempts you not all to describe it, the main decorative feature being a juke box. You continue to tear and dip and bite, at last continuing just because you haven't found a natural stopping place. And that's it. Plus a bill of less than $5 a person. Mamma Desta could be the mother of the year.

People think of the Serbian Crown as a Russian restaurant, Cafe Lovcen as a sandwich shop. But if they look beyond the caviar and kulebiaka at the Serbian Crown, and upstairs beyond the lunchroom at Cafe Lovcen, they will discover Washington's two Yugoslav kitchens. They will also discover that the difference between a luxurious Yugoslav meal and a passable one can be but a few dollars.

Cafe Lovcen has edged towards stylishness as it edged upstairs. The largest second-floor room bounces a golden glow from its yellow lamps to its yellowish walls to its nearly yellow plastic tablecloths. Central tables display wines in baskets on one, paper flowers and folk-costumed dolls on another, with a few Balkan-looking pastries wrapped in plastic. Fresh flowers are on some tables. In all, the dining room is dim enough to seen festive, whatever the seams that show in its fancy dress. The waitresses are robust and energetic, keep apologizing for slow kitchen, leave you to your own devices between apologies. The food could be better.

Aside from universal fares such as trout and steak, the menu lists fewer than a dozen Yugoslav dishes, several of which differ from each other only by being of lamb than pork. The important thing to remember is to order scampi, either as an appetizer ($3.25) or main dish ($5.95). The scampi themselves lack flavor, but that is overcome by being sauteed with onions, peppers, tomatoes, garlic and parsley into a bright red and green crunch. After that it is a savorless choice of raznjici - vinegared and herbed cubes of pork or lamb cooked nearly dry and bedded on a mush of orzo (rice-shaped noodles with bits of onion, mushroom and green pepper) - or cevapcici - compact cylinders of ground meat lightly spiced with salt and pepper but not much else, served on the same orzo, along with frozen peas. Other Yugoslav possibilities also miss the mark. Best of the main dish accompaniment was potato salad, sprightly with black pepper and vinegar.

Fatigue has set in at Cafe Lovcen, at least in the kitchen. The rolled pastries wrapped in plastic taste like their wrapping, now that their apple butter and nut filling has been reduced to hardly a smear. Even the coffee is weak.

An infusion of energy at Cafe Lovcen could do wonders. Its food is, indeed, homemade, and the flaws seem to be peripheral - overcooking here and there, a stale taste to this and that, stingness from time to time - while basically, fresh ingredients are being used, and the seasoning show competence. The scampi, sausages and potato salad give one hope.

Admittedly, the Serbian Crown is another sort of restaurant altogether, a Serbian-Russian restaurant of elegance and sophistication, with the prices such surroundings and service warrant. In the Russian tradition, it serves 18 different straight vodkas, fresh caviar from Russia, Iran and Canada, a glorious array of lamb, veal, beef, duck, suckling pig and lobster and - the highlight of the menu - kulebiaka of salmon of its food, Serbian Crown is one of the most interesting places you can spend $30 for dinner.

It is also the place one should try Yugoslavia's simple cuisine (though the Russian cuisine offers even greater temptations). Here the raznjici combines pork and veal on a skewer with onions and bacon squares, the whole lightly seasones and grilled to a state both crisp-edged and succulent. A mere spoonful of thin brown sauce, a hefty portion of delicious garlic-buttered fresh green beans, and a mound of finely chopped onions finish the plate. Though it is less delicious, the cevapcici is similarly presented, the serving - like the raznjici - enormous, the seasoning rather restrained. Each of these Yugoslava dishes is $5.50 at lunch, $7.95 to $8.50 at dinner, and the inclination, with such an elaborate menu and wine list is to spend considerably more than would at Cafe Lovcen. But on a dish-by-dish basis the quality and quantity of Serbian Crown's Yugoslav food is a better buy. Go ahead and splurge on the strudel.

More than a grocery, less than a restaurant, Bayon Market consists of six brown Formica tables (each with a silk flower), two pinball machines and a kitchen the size of a small desk. Fittingly, its menu consists of notices posted around the chechout counter announcing the availability of "pork or chicken on top of rice," "chicken amok (Cambodian specialty)," tuna and BLT sandwiches, and roasted duck (only a myth, if my visits were typical). A careful search of the premises and a few questions will turn up other eating possibilities: Chinese-style egg roll (soggy), tiny Cambodian egg rolls (bland), flat cold dumplings of a unique rubbery texture with bits of meat and remind one of chopped liver, a taste that it is possible to acquire over a long evening. You can also buy giant burlap bags of rice or T-shirts, but they are only sidelines. Having plowed through the full variety of hot fried fish cakes (salty and greasy), apparently nameless sweet and savory plastic-wrapped surprise packages (the sweet one exceedingly sweet), aptly-named minute chicken (forgettable), I can confidently announce one reason to visit Bayon Market: a foil-wrapped bundle, chicken amok, is a kind of steamed chicken pudding unlike anything esle you may have tasted, and requiring no leap of faith at all to enjoy. It's custardy texture is studded with pieces of chicken and shreds of Chinese broccoli leaves, its top decorated with strips of pimento, its aroma pungent with ginger, its flavor faintly sweetened. Bayon Market has hopes of a liquor license, of expansion, of redecoration. Fine, as long as they keep steaming that chicken amok.