When I go to DC,I usually stay in Rosslyn, which is just across the river from Georgetown. If you watch Emerald Robinson on Newsmax, she often reports from a place high over Rosslyn. The red-brick apartment complex where I once lived is in the background.
I have also stayed in Ballston, which is a couple three stops on the Metro beyond Rosslyn, and this is a nice and safe area.
what about coming from BWI ?