High Valley Road to Hayfield Road
High Valley Road is the intersection nearest the large tree. Turn right and take High Valley for about a quarter mile -- bear right at the first split in the trail -- to Hayfield Road.
Hayfield Road passes between an old barn on the left and a picnic shelter on the right. It then curves to the right and heads downhill for about a mile back to the bottom of the hill near Alameda Creek. See if you can spot a cactus grove on your right on the way down; with any luck a cacti might be in bloom.
At the bottom of the hill, turn right, go a short distance and turn left at the bridge returning to the Park HQ.