Agate 1, 6551 Riggs Rd., Hyattsville (near East-West Highway). 422-7766.

Open Tuesday through Saturday, noon to 8 p.m. (Friday until 8:45 p.m.); Sunday, noon to 7 p.m. Prices: Main courses average $2.50 to $3.; Agate 2, 6521 Riggs Rd., Hyattsville. 559-8558.

Open Monday through Saturday, 11 a.m. to 10 p.m. No credit cards. No reservations. Prices: Sandwiches, $1.40 to $3.80; platters $2.85 to $5.95.

JUST as San Francisco air produces that city's unique sourdough bread and the caves of Roquefort nurture the specific bacteria which foster that locale's special cheese, certain geographical settings seem to encourage particular kinds of diners. Cincinnati breeds sophisticated diners; Boston rears adventurous diners; Prince George's County raises loyal diners.

An announced search for good Prince George's restaurants was answered with a flurry of calls and letters, and I am still making my way through Laurel and Adelphi and Suitland in their wake. So here is an interim report. Just let me say that to get to this stage took eating the likes of tenderized veal in tomato sauce, flamed with Tennessee sour mash whiskey, followed by the house special dessert of canned fruit cocktail in Tennessee sour mash whiskey. Several people not only considered that restaurant the county's best, but took the trouble to call or write me about it; they are indeed loyal patriots of Prince George's.

So I persevered. And I found that one of the major events in Prince George's in the past couple of years has been the expansion of Casa Baez from a carryout to a carryout with a dozen or so tables.

Casa Baez, having had some early relationship with the District's Omega restaurant, has been a carryout for several years, and catered dinners that were remarkable bargains. For about $3 a person they would send pans of crisp-edged pork masitas, dense piquant shreds of beef known as ropa vieja, chicken roasted and then fried and permeated with vinegared onions. Always came the giant containers with rice and black beans. And to round out the meal were faintly sweet fried ripe plantains and desserts of caramelized puddings.

It is all still bargain-priced and generously portioned. The food is still earthy and savory. Only now you can order your dinner at the counter and carry it to a table in the square room bordered in knotty pine-looking plastic paneling, at wood-grained Formica tables, and wash it down with a cold can of watermelon or sangria soda, or a sweet, beer-flavored soft drink called malta.

Casa Baez has no liquor license. It has no late-night hours. It has no quaint charm. It has no waiters, no coat rack, no tableware except disposable plastic. It does, however, have good food. And its prices are cut so close to the margin that a handlettered sign warns: "Bread 12 cents; butter 4 cents."

If all you know about Latin American food is tacos, you can do fine at Casa Baez. They are stuffed to the edge with chicken or beef (60 to 85 cents) and rest on a bed of onions and lettuce. The cheese on them is a disappointing pre-grated dust, but the meat is admirable -- moderately spicy, shredded, freshly cooked. Besides chili, omelets, pickled fish and small, cylindrical chicken croquettes, the appetizers include meat-stuffed dough steamed in envelopes of leaves or parchment. The most familiar are tamales (70 cents)8 but Casa Baez also makes a white cornmeal version called hallacas, and dark green, glutinous plantain versions called pasteles. Stuffed with meats and accents of olives, raisins, capers and chick peas, they may be considered acquired tastes, but good versions of the art.

Main dishes at Casa Baez range from $2.35 to $3.10, except for paella and its all-seafood variation, arroz con mariscos ($4.55 to $4.75). Stick to the lower price range, discovering the pleasure of onions cooked to melting in vinegar, a perfume that permeates the fried pork cubes and roast chicken. Try the forerunner of the sloppy joe, picadillo, its ground meat seasoned with a little red pepper, a lot of paprika, and olives. Or sample Mexican-style chicken, peppered with restraint, seasoned with cumin and paprika and paprika and shredded into long, moist hunks. It costs all of $2.35, or $2.60 if it is wrapped in corn tortillas to make enchiladas. This is filling food, especially when downed with the authentic portion of rice and black beans, and a side dish of plantains. The flavors are robust rather than subtle, but far from the stupefying fire of Tex-Mex food. With a tiny aluminum cup of pudding for dessert -- the golden, caramelized flan is better than the dense bread pudding, and the occasionally available creamy rice pudding beats them all -- you will easily get change from a $5 bill, and can probably skip your next meal.

In order to do that, you will have to drive very quickly past Carzy Horse Bar B Q Ranch, down the street.It, too, is a carryout with a couple dozen tables. It, too, dishes up some startling bargains.

The magnet is the chimney, the badge of a barbecue worth stopping for. Inside it is clearly a classier operation than Casa Baez; its walls are painted raspberry, and are studded with a few Western knicknacks. It has a bar and checkered curtains, a few hanging plants, and even ahigh chair. It has a juke box to keep you entertained while your barbecue is being sliced or chopped. And it has a menu littered with unnecessary complications. Who needs crab cakes at a barbecue? And what is a DELUXEITALIANHOGIE doing in a smokehouse? You are here for barbecue. Don't get sidetracked, except for an order of fried onion rings (95 cents), because there are so few places left (all of them in Prince George's County, I think) that still slice and batter them fresh.

On to the barbecue, the ribs and the sliced pork or beef and the minced beef. It is highly smoked and lightly sauced with a predominance of vinegar and a little hot pepper. You might want to add a few shakes of Tabasco if you were raised in the Southwest. The ribs are brushed with a sauce that is too sweet (a fact) and too tomatoey (an opinion). But it is undeniably real barbecue. Even better than the ribs are the juicy sliced beef brisket and the minced pork with crispy bits of the crust chopped in.

So, you say, it is nice to hear about another barbecue place. This, however, is only part of the tale. The punch line is the prices. A barbecue dinner costs $4.25 to $5.95. A minced pork sandwich, mounded on a hamburger roll with a smear of coleslaw, costs $1.40. And that peculiar construction, a rib sandwich, costs $2.50 and consists of two sodden pieces of white bread trying to cover no less than seven ribs. That, plus a quarter for the juke box, is a good cheap batch of pleasure.