I come from Falls Church, not Alexandria, but work across the street from the Reagan Trade building. I'd just cut across the National Mall once you get to the Holocaust Museum. You can cross Constitution at 12th Street. There is less car traffic and a it is a little more scenic. If you do this, the Reagan building is about half way between Constitution and Pennsylvania on the left side of 12th Street, near the Federal Triangle Metro stop.

The Summit is not free but I have to work those days anyway. However, the Adventure Cycling Association is having something on Wednesday night after work for its members which I am going to attend.