Santa Ysabel truck trail can be ridden either direction. West to east starts with a stiff 1.5 mile climb. Followed by 3.5 miles of up and downhill. Return trip makes the initial climb into a fast and fun, but not technical, descent. This is jeep trail all the way; usually open to motor vehicles, so beware. But it is occasionally closed to motor vehicles due to trail conditions; mud mainly, but can have serious road wash-outs after rains--- serious enough to swallow large 4x4's or mtb'ers who fail to look far enough ahead. And by the way, this is mountain lion country---I don't like to ride it close to dusk or after dark (unless I am with a group with slower riders;).
From Kirk's Bike Shop in downtown Ramona: 6th north to A St, left to 7th St, right to Elm St, right to Haverford Rd, right to Pamo Rd, left, continue down Pamo Grade (45 mph coasting on an mtb!) to intersection with the truck trail on the right at about 7.5 miles total from the Kirk's. Note: a Forest Service Adventure Pass is required for parking along Pamo Rd, as this is in Cleveland National Forest.
http://www.singletracks.com/item.php?c=1&i=10377