Usually I don't watch Dolphins games until the Florida Marlins' season is over, because their sunday games often overlap.
Last night though I went to ESPN Zone near the MCI Center. The good: centrally located between Catholic, Georgetown, and George Washington Universities, HUGE TV, and a couple groups of Fins fans. The bad: Awful service (cold baked potato, ran out of everything) and atmosphere.
I'll probably try the Park Bench Bar near UDC and American U in Cleveland Park next time.
Also if you're looking for a place with vegan or kosher options, try Asylum in Adams Morgan. Been there a few times, not many Fins fans, but good service.