Taqueria Tres Reyes
Taqueria Tres Reyes, 5403 Kenilworth Avenue, Riverdale, MD, 301-779-6060 (Metro Trip Planner - opens in new window) [WaPo | City Paper | Don Rockwell (also see this) | openlist]
On weekends they open at eight in the morning, as a good Mexican place should. Fully authentic, the shrimp soup is wonderful. Huaraches are tasty too. Superb for atmosphere and people watching, even when the jukebox is a bit too loud. Recommended.