I think you are underestimating DC's public transportation system. SAIS, being right next to DuPont Circle, is easily accessible by metro and bus at basically all hours. In fact, one of the Georgetown shuttle stops is in DuPont Circle. That said, pick the school that's best for you, not the school that has the best commute. You don't want to base your professional career on a 30 minute commuting difference or small amounts of rent difference, and you can make things work if you need to.