check this the night before:

http://www.metwashairports.com/reaga...on_4/parking_2

if there are a reasonable number of spaces available, drive. pick a major/minor road from 29 that will get you very close to airport(glebe comes to mind). i will really be surprised if there are many people up and around.

i would stay away from all metro stops. i think they will be a zoo. people will be trying to get into the non spaces.

buses will be running. is there a bus to dca from someplace in va that you can get? i am not familiar with bus transit in va.