Let me be the first of the DC crew here to welcome you to ENworld!
There are a number of groups in the area, many concentrated in Alexandria/Springfield, but I think there is a crew in Bethesda or Rockville, I forget which.
I live in Loudoun County, but the commute around here would make me getting to those areas about 2 hours one way, so the traffic, especially around the Beltway, can be a real pain. If you have easy Metro access, one of the groups mentioned above would be good.
There are also a number of small to medium gaming stores throughout the Metro area. On the VA side, Game Parlor in Chantilly is a popular spot and is probably the most oft referred to on my side of the Beltway.
So that should at least give you some hope. Again, welcome to the area, and don't hesitate to check out the Living Worlds here at ENworld. Forum hosted 'continuous' games where your character gets a chance to grow, meet other characters and have adventures under a number of GMs.