The Pleasanton Ridge Trail is a multi use trail which follows along the ridge line which is West of the 680 Freeway.
The trail is fairly well used and there are quite a few hikers/ horseback riders and other bicycle riders on the trail, especially the during the 2 mile climb up the the ridge. Once you are up on the ridge there are fewer other trail users and there are miles of rolling hills with great views of Pleasanton and the area surrounding the ridgeline. You get a great workout riding here and the on the downhills you can easily reach speeds exceeding 30 Miles Per Hour. Watch for other trail users as collisions at these speeds are no fun.
This trail is much more interesting as a night ride.
Pleasanton Ridge trail is not a technical trail. Although the rolling hills and return trip to the car is fun and fast it is not particularly difficult. If you want challenging singletrack, go elsewhere.
I followed these Instructions to get there. Basically take 680 towards San Jose and take the Pleasanton-Sunol Blvd. Exit. Go west and take the next available right onto Castlewood. Follow Castlewood to next left onto to Foothill Road. Follow Foothill approximately 3 miles to the Pleasanton Ridge staging area on the right.