Traffic sucks, period. If possible, metro.
Rent for a one bedroom, depending on where you are in and outside of DC, can range 1100-2000 and up. You can find a nice english basement type deal in upper northwest for 1200 if you look hard and act fast. If you want to have a car, live outside of DC...parking in DC is ridiculous, and expensive. I would not live in the eastern half....it gets scary over there...NW and SW only. I live in crystal city, which is just over the 14th street bridge in arlington...I like living out here better...I'm five minutes from the city and don't have as much BS to deal with when it comes to parking, taxes, etc. It's not much less expensive to rent out here, though, unless you're willing to have a roommate, in which case you can usually get something that, when split, is in the 600-800 range.