It's easy to get around DC by public transit most of the time. Driving there from Williamsburg, Va is a big pain in the arse because of traffic on I-95. The last couple of trips (primarily spouse work related) we've used AMTRAK from Richmond. Parking is reasonable ($10 a day, compared to exorbitant DC rates) and a 2 1/2 train ride. Maybe $35 if you book business class.