http://www.madamsorgan.com/
Was just there Tuesday night after the inauguration... def. a good time. There is a stage on the first floor where they usually have live Blues playing all night with lots of eclectic things hanging from the ceiling. There is a half level near the back with bars on each level. The second floor is a more loungie area with another bar and a bit more upbeat music playing from someones media player or an unseen DJ. Up another set of stairs there is a technically outdoor but it feels (temperature wise) indoor tiki bar where you can smoke and order more drinks. On the other side of this floor there is yet another bar that was playing some swing music. This place would easily handle a large group (5 bars 3 levels lots of bathrooms) and their various tastes.

Besides that, I would generally recommend places around the Adams Morgan and DuPont Circle areas. Both of these area's are off the red line and would be less than a ~15-20min metro ride from the Convention Center.

All on H st NE, a short bus ride from the convention center.

Vegetate up 9th street from the Convention center is also very good, vegetarian friendly.