To get to River Run from downtown Davidson, drive (or run or bike) east on Davidson-Concord Rd. and veer right at the Hwy. 73 sign. Once past the Bradford subdivision, turn left onto Robert Walker Dr. Parking is available across from the soccer/baseball field.
Here is a MapMyRun map of one of my recent runs through the area. It starts at the soccer field and goes to the other end of River Run, which currently terminates at Shearer Rd, and then back to the start.