Open Monday through Saturday from 11 a.m., Monday through Wednesday until 6:30 p.m., Thursday through Saturday until 7:30 p.m. AE, MC, V. Reservations.

We all know about lunch. In fact, we all know too much about lunch, that daily break in routine that in itself becomes routine. The lunch break, the working day's big chance for adventure, is also the make-it or break-it time for a substantial proportion of downtown restaurants. Thus they, too, fall into routine, daring not the risk of losing the hamburger crowd or the chef-salad diehards.

But downtown - Washington's old E and F street department store corridor from Hecht's to Garfinckel's - is making a lunchtime comeback. Not only are there new restaurants, but new kinds of restaurants, and in one case a renewed kind of restaurant. Here are three that might even eat into the Reeves routine.

You can't eat nostalgia, but the Blue Mirror has enough of it to help make food more palatable. Long, railroad style corridors lined with, of course, blue mirrors above the blond Formica booths are Art Deco heaven. The neon sign that says "Cocktails," the coat hooks on the corners of the booths, the dance hall cups and saucers: it is the kind of place where you expect a Hollywood producer to discover not the starry eyed young waitress, but the crockery. Even the two tonedhunks under opaque ivory gravy have an Art Deco look.

But you gotta eat. That's the problem.Despite new management the turkey sandwich ($2) consits of spongy factory fresh meat on flismy rye; the dry roast beef ($1.95) is an even gray; the corned beef ($1.95) is recognizable primarily by its color. At that, the waitress warned us against the daily special and the carrot cake. What the restaurant pushes is a "flame broiled 8 oz. New York Sirloin Steak, Salad, One Veg, Roll & Butter, $5.55," and it is not a bad buy, though the salad and veg are as forgettable as the sandwiches. The meat has a little chew to it, but flavor, too. And the waitress is cheerful about returning a too rare steak to the soup is a little curdled and not worth worrying over.

It all comes out well in the end if you kept your eyes opens when you walked in. If you ignores most of what the menu tells you about desserts. If you order the strawberry shortcake ($1.15) that has decorated the Blue Mirror's front window as long as most Washingtonians can remember. The waitress asks you if you want it with juice, and you say yes, and you get a bowl with a big pieces of yellow sponge cake layered with honest-to-goodness whipped cream and strawberries, with strawberry juice poured over it and soaking into cake and whipped cream. Maybe downtown has a chance after all.