Open Monday through Friday, 7 a.m. to 3 p.m. and 5 to 10 p.m.; Saturday and Sunday 7 a.m. to 10 p.m. Some days open later. AE, BA, CB, D, MC, V. Reservations except on weekends. Breakfasts average $3.25; lunch main courses average $4 to $5; dinner main courses average $6 to $9.

After you have been to enough pinata parties, you realize that the thrill is in the event itself rather than the content. The suspense, the mystery, the vividly colored shaggy paper animal, the drama of battering the pinata with sticks until it bursts and showers its candies on the waiting attackers - that's the reason for the pinata party. The candies themselves are usually no more exciting than the peppermints in a bowl at the exit of a restaurant.

La Casita is Washington's pinata party. We waited nearly a year for it to open, peering in the windows to see the colorful mysteries waiting for their stage lights. And now that it is open, the interior looks every bit as irresistible as a fringed paper pinata. Mexican tiles in every color, in dozens of geometric and floral shapes, creep up the walls and group into small dining tables. Whatever is not painted tile is painted wood or curved clay roof tiles. Even the food is red and green and flower-shaped and artfully arranged. Tortillas are presented in a small basket topped with a miniature sombrero. Tostadas, a basketful offered with hot sauce as you are seated, come in two colors, though the rosy ones taste no different than the more familiar corn-yellow ones.

The menu reads like a fence covered with posters; In addition to 20 mix-and-[WORD ILLEGIBLE] combination dinners and 12 grilled meat choices and two pages of a la carte items (five kinds of chiles rellenos, 16 different tacos, for instance) the pages are crammed with descriptions, [WORD ILLEGIBLE] and warnings. One star designates "very popular among chicanos in the Southwest." (no similar attention paid to Southeast or Northwest or gringos), except when it designates "allow 15 to 20 minutes." Two stars means "recommended for vegetarians." The men also brags, "We start from scratch" as well as "no frozen foodstuff." Furthermore, it insists, the dinners are "indescribably delicious as cooked in the Southwest."

Among this officialk graffiti is a full encyclopedia of Tex-Mex dishes - burritos, enchiladas, tamales, quesadillas, chimachangas, taquitos, chalupas - a few less prevalent dishes. There is, for instance, the chili-flavored tripe soup called menudo, and tacos are either the usual crisp ones or more unusual soft, puffy tacos, the shells reminiscent of Indian puffed bread. And one whole page is devoted to steaks and barbecues; on weekends there is pit-barbecued brisket of beef and charcoal-cooked baby goat.There are beers from Texas and Mexico. And, as if all that didn't offer an eclectic enough choice, lately there has been a special dinner of tempura - yes, tempura - with tripe soup, chicken-filled turnovers, sopaipillas for dessert and after dinner liqueur, all for $10 to $12 a person.

While the tempura dinner is a good buy, its appearance on a Mexican menu denotes a certain uncertainty in the operation. The reason given for this ethnic mishmash was that the chef is a Thai woman. But the confusion appears throughout La Casita. I asked the waiter one day about the difference between the combination platters and a la carte dishes; he inisted that the combination dinners were better - better cooked, from better ingredients - than a la carte. The next visit, another waiter was more direct, simply explaining that on weekends no a la carte orders were served. He, however, was confused about the contents of the "Mexican Tempura Special" and forgot our dessert, besides bringing the after-dinner liqueurs in the middle of the meal and main courses before appetizers. Willingness outweighs competence at La Casita.

Getting to the contents of this vital, lively pinata of a restaurant, the food is good, but not always as good as the prices imply. The tortillas taste fresh indeed, and form into good, grainy wrappers for tacos and enchiladas and the like. But the fillings lack the zest to make them either memorable or wortt $2.50 to $3 per taco for the "special" ones or $1.75 to $2 for the regulars. Most of the a la carte items are $2 to $3, so a meal constructed to order grows expensive. And combinations, since they come with refried beans (stiff and dull) and rice (decent pinkish stuff), are even more expensive, the least costly being a single empanada for $4.65. Barbecue prices escalte to $11.45 for a mixed grill or for baby goat, which tastes parboiled and dry, with neither charcoal flavor nor other discernible seasoning. The menu has some clear winners: the empanadas enclose teasingly scented meat in excellent flaky crusts. The tripe soup is fragrant and rich. All the tortilla-enclosed dishes are meaty and substantial, if not exciting. And the charcoal-grilled skewered maybe are piquantly marinated. Dinners end with a flourish of honey-drenched, crisp and delicate sopaipillas and glorious thick hot chocolate. But you can miss by a mile if you bother with the tempura or the goat. And the brabecue, while its charcoal flavor is tempting, also tastes parboiled and stringy, its sauce, if you order it Texas style, too sweet for a Texan. Tamales tend to be dry and crumbly, guacamole pasty smooth and underseasoned. Sangria is warm and sweet as if it came premixed from a bottle.

Thus, what rains down from this pinata is Mexican food of notable freshness and substance, though lacking the personality that turns the uncommitted into Mexican food freaks. Given the surroundings of such considerable delight, La Casita can turn a feast into a fiesta. But the price is high for Tax-Mex food; a tour through the menu can easily total $15 a person, washing it down with beer, sangria or margaritas. It's worth it if you pick and choose, but not if you grab whatever dishes catch your eye.