Ben's Chili Bowl -- overrated and only worth it if there's not a mob scene
Lauriol Plaza -- mediocre tex-mex fare, a favorite locale of the type of herd-following people who'll go to a restaurant simply because there's a line outside, and more importantly for this thread, nowhere near the 9:30 club
Polly's -- has gone way downhill
Black Cat -- decent lasagna, burgers, vegan food
if you're the adventurous type, there's a carryout restaurant on 9th Street just south of U which has great Moroccan food at a reasonable price, as well as more standard fare. There's a Pakistani carryout place on U Street, somewhere near 13th, which has some good spicy south Asian food as well as the obligatory giant pizza slice. Decent Ethiopian food at 11th and U. There are a bunch of decent restaurant choices nearby but I think the original questioner is looking for something cheap and quick.