Don’t forget, your best chance to see pro cycling in the DC area will come tomorrow at the CSC Invitational. 
Racing starts at 8am, but if you just want to see the men’s pro races, show up around noon. If you’re taking Metro, you can emerge in the center of the circuit at the Clarendon Metro stop. It’s pretty easy to move around the circuit as the race progresses, but my two favorite spots are on the western-most edge of the course (standing in the middle of the Wilson/Clarendon/Washington Blvds. intersection (it will all be closed to traffic)), and the corner of Washington Boulevard and North Highland St. (stay back from the edge, though – it’s a common place for crashes, and there are no crowd barriers to protect you). The most recent pro start list is here. Come check it out.
