You will enjoy DC. As to transportation, there is a Metro Station just about every block. We stayed in Virginia and took the Metro to DC. You just have to remember your "colors". The concierge at your hotel can give you infor on the "to dos". Actually our hotel has a shuttle bus which would take you most anywhere you wanedt to go with a reasonable radius. Such much easier than driving. We parked our car at the hotel and didn't even use it the whole time we were there.
Have fun and congrats to your GS!!