I've tried quite a few places up and down 18th ST and Columbia Rd. Just wanted to laud a few places that I haven't seen praised much.
Bukom Cafe (18th ST). Awesome. Unique and unusual cuisine (Ghanian), delicious food, and good prices. What more can you ask for? Well, perhaps you could ask for a more calm dining environment sometimes (one night we walked in and it appeared that we had stumbled in upon a party in Ghana), or more alert service. But these are minor quibbles. The pepper soup is one of the best soups I've ever had. Try it with smoked fish. And the chicken in peanut stew is absolutely awesome, as is the fish with okra. Kenkey (fermented cornbread) is worth a try for the unique flavors it offers--I admit I have to get used to it.
Santa Rosa Seafood (18th St). The breadth of the seafood menu is fantastic, and I can't wait to go back--only been here once. I had the seafood paella, which was wonderful. The generous portion of rice was rich with the flavors of the wide variety of fresh seafood--a half lobster, clams, shrimp, scallops, squid, and fish. The complementary chips and salsa were also quite good.
Pollo Granjero (Columbia Rd a few blocks east of 18th St). It's not fancy--it looks a little bit like a Salvadorean Burger King inside, and it's self-service. But appearances are deceiving. The food is actually very good and a tremendous value. I adore the $1.50 pupusas, which are much better than the ones I have had at El Tamarindo and elsewhere. Three pupusas (that come with mayonnaise-less cole slaw) might constitute the best <$5 lunch in DC. But the rest of the menu is worth trying. The plaintains with cream and frijoles is delicious, the yuca fries are good, and the casamiento (red beans and rice) is a fantastic value. I have been told the fried chicken is very tasty. Given $10 and a big appetite, I can't think of any place in DC comparable in quality and quantity to Pollo Granjero. Indeed, $10 would surely be gluttony.