Lake Poway is a singletrack loop around the lake and behind the Damn. around the lake is a nice XC ride and behind the damn is a nice DH with switchbacks. once your at the bottom you have to ride up the other side. ugh.
From Interstate 15, exit Rancho Bernardo Road, travel east to Lake Poway Road, turn left and follow park entrance to gate. $5 per veh for parking
http://www.singletracks.com/item.php?c=1&i=3750