Proceed to University Dr., go left, the Fieldhouse is on the left. Parking is very limited. Try the area around the Kennedy Center or in Georgetown, then walk down to the river. Alternately, you could park in Rosslyn and watch from the Key Bridge, which is 1000m into the 1500m course. This is a unique vantage point and gives the opportunity for great photos.
School is on the corner.
Right onto Eldon Street. LEFT on Dranesville Rd. LEFT on Bennett Rd. School is on the Left. School is on the Right.