On a beautiful sunny day I met a friend for lunch at her favorite neighborhood restaurant, Pierre Alber. Patisseries, delicatessen meats and fish are sold inside, and salads, omelettes and sandwiches are available outdoors under an awning. The prices were so reasonable, and the omelettes and salads my friend and I ordered so well prepared, I thought I'd return with my family for an inexpensive al fresco French dinner.

My husband was skeptical. "Cheap chow mein can be good; cheap pizza can be terrific, but inexpensive French food?" Against his better judgment we set off for Pierre Alber's on a warm and beautiful Friday evening. Everyone was in the mood to sit outdoors and enjoy the evening meal.

Unfortunately, several people had the same idea and when we arrived at 8:45 all the outdoor tables were taken. Chins drooping, we headed indoors where there were three rows of tables, all but one of them empty.

On a rainy day, the inside of Pierre Alber, with a gay umbrella cart in the corner, would not be without charm. On a beautiful summer evening the formica-topped tables were a downer. However, along the partition that separates the patiserrie and delicatessen-style counter from the restaurant were stacks of old magazines. Our children searched for the oldest magazine in the collection while we consoled ourselves with a half carafe of wine.

The menu is extensive enough to offer a dish for almost every taste. The soups ranged in price from $1.75 to $3.65 and in selection from gazpacho to La Bourride, a potpourri of mussels and fish. The French dishes sounded exotic with such dishes as koulibiac, salmon en croute with mushrooms and white wines for $3.95 and Croustade auxs champignons, mushrooms in cream and wine sauce in a puffed pastry, for $3.25. If French didn't appeal, there were Italian dishes that ranged from $3.45 to $3.95, or omeletes for $2.95 to $3.95, the top of the line being a Moishe's omelette with lox.

In addition there were sandwiches, both simple meat sandwiches for $2.65 or more involved concections such as Le Piednoir (subtitled, Munster Bunster), which features muenster cheese and egg on pita bread, $2.95. The salads were similarly wide ranging.

After many debates about what would be good, followed by many changes of mind, our daughter, 12, ordered a special of the day, beef burgundy, at $4.25, plus a small dinner salad, 75 cents. My son, 10, chose onion soup, $2.25, plus a roast beef sandwich, $2.65. My husband threw his caution about inexpensive French food to the wind and ordered stuffed mussels, $3.25, a small salad and onion soup. I opted for the trout on a bed of spinach, for $3.95. Bread and butter was extra, priced at 40 cents per serving.

The onion soups were the first test of my husband's theory. They were passable - highly seasoned, thick with onions, cheese and bread. The salads were crisp and dressed with a very nice house dressing. So far, so good.

The next course was more of a mixed bag. My son's sandwich was superb - pink and juicy roast beef on good rye bread. Not French, but very good. My trout florentine, breaded and fried, was also well prepared and good. The beef burgundy teemed with noodles, mushrooms and meat. My daughter liked it and had more than enough to give everyone a generous taste. It wasn't the greastest beef burgundy, but it was good enough.

The mussels were not. They had been overcooked to a point of toughness and not all the butter and herb stuffing could save them. They confirmed, in my husband's eyes, his theory about French food. The rest of us, however, felt we had a good meal.

Desserts were something else. A refrigerated case held eclairs and cream pastries of every variety. On top of the counter sat row upon row of turnovers and buns. Our waitress, sensing that our children might not give the dessert they wanted the right name, suggested they follow her to the dessert case and make their selections on the spot. They returned with two of the richest desserts in the collection: a strawberry custard tart and a three-tired concoction of puff pastry, carmel icing and custard stuffing. My husband and I chose simpler desserts: a raisin bun and a cherry turnover.

The desserts, which came to a total of $2.55, proved that inexpensive French pastries can be absolutely superb. If we'd been able to eat outdoors, they would have wiped out all memory of the mussels, as well. Our tab for dinner, which included several. Cokes, milks and wine, came to $31.75. Pierre Alber Gourmet Shoppe

5018 Connecticut Ave. NW. 966-8501.

Atmosphere: Inviting outdoors sidewalk cafe; simple indoor room brightened by a patisserie.

Price range: $2.65 for sandwiches to $4.25 for French specials of the day.

Hours: 10 a.m. to 10 p.m. Tuesday through Friday; 9 a.m. to 11 p.m. Saturday; 9 a.m. to 5 p.m. Sunday. Closed Monday.

Special facilities: Accessible to wheelchairs; booster seats available.

Reservations: Not available.

Credit cards: Cash or personal checks only.