There's no telling what you're going to find at Chapultepec Mexican Restaurant (813 Richmond, 522-2365). The last time I was there, a Howard Stern look-alike -- or then again, it might have been the man himself -- sat slumped in a corner; and the time before that, someone was playing selections from Hair -- "Good Morning, Starshine," and all that drivel. The only thing predictable at Chapultepec is the food. Which is always predictably good. The enchiladas verdes ($7.95) never disappoint. There are three to a serving, and you get to choose the filling: beef, chicken or spinach. Or, if you prefer, you can have one of each. Or, say, two beef and one chicken. Or two chicken and one spinach. Or.... But you get the idea. And if you don't, just consult your waiter.