Hours: Open for lunch Mondays through Fridays, 11:30 a.m. to 3 p.m.; dinner, Mondays through Saturdays, 5 p.m. to 11 p.m.; closed Sundays and holidays.

Atmosphere: Mexican villa.

Price range: From $5.50 for chili to $10.50 for paella.

Reservations: Yes.

Credit cards: All major cards.

Special facilities: Entrance is down a flight of stairs. Booster seats. Near Dupont Circle and Metro transportation.

When you walk down the steps out of the cold wintry night into La Fonda, you quickly forget the week's headaches and fall under the spell of the restaurant's charms.

The two dimly lit dining rooms transport you immediately into the heart of a thriving Mexican establishment. Blue-and-white tiles line the walls and village memorabilia are displayed throughout the room, including a mounted bull's head that overlooks the well-spaced, cloth-covered tables.

Somehow La Fonda has managed to combine the formal with the casual. Three-piece suits and jeans appear equally appropriate.

While we were studying the menu, our water glasses were quickly filled and a basket of light tostadas arrived with two sauces, one spiced lightly, the other a bit more.

We discovered a number of wonderful dishes, although the children were more enthusiastic about appetizers than entrees. Our son began with soup (sopa de lima, $1.95), which was a perfectly seasoned chicken broth with noodles.

For his main course, he selected tacos Mexicana ($2.95) from the appetizers. He could hardly wait until his two beef-filled tacos arrived. Unfortunately, the kitchen topped them with cheese, which ruined them for a non-cheese-eater. Although it looked pretty, our son was devastated; he needs to remember to say, "No cheese, please," in future orders.

So we traded. The tacos were fine: nothing spectacular, but amply filled and still crisp.

In exchange for the tacos, I gave up the evening's special--flauta de hacienda ($5.95). It was superb: a crisp, light fresh tortilla stuffed with spicy beef and topped with a creamy guacamole. A portion of Mexican rice and refried beans filled the platter.

Our daughter's order was more successful. She began with a dinner salad ($1.50), which came with an avocado slice and a perfectly seasoned house dressing. The empanditas ($2.75), which are similar to turnovers, lacked their light fluffy texture, but were nicely filled with spicy beef.

The two other entrees we ordered were equally good. The carne asada a' la Mexicana ($7.95) was a generous marinated and charcoal-broiled steak that was beautifully presented with guacamole and Mexican rice.

Similarly, the chicken mole combined spices and chocolate into a perfect topping over baked chicken pieces ($6.95).

While the children had soup and salad, we all sampled from our evening's one adventure: cactus salad ($2.95). With its vinegar dressing, the salad reminded us of a marinated bean salad and was not as different as you might expect. Even the children bravely raised their forks to try it.

Flan and guava are dessert choices, but we were comfortable with our large, skillfully prepared dinners. Coffee was the only finale we required.

Even with a bottle of Mexican rose' wine, sodas, tax and tip our evening for five cost $49.60.

There is something graceful about La Fonda. Instead of growing old, it carefully performs its magic more skillfully each year. No wonder weekend reservations for late dining are a necessity.