Slate - seriously, if you are talking rush hour from Crystal City, metro to Lenfant or archives and the green line back out is less than 25 minutes. Very good connections, and you only haveto deal with a straphanger who forgot to use right guard for the green line stretch.
Going home is a nag, but I'm usually back in CC in less than an hour.
I'll give you something more creative - is there a red bike rental drop off near the stadium? Grab one and prove you are as much of a biking stud as MDS.