Marty Minshall trail features some nice, easy singletrack down along the shore of Lake Cuyamaca. There's a small trailhead/parking at the bend in CA79 where it intersects Milk Ranch Road
. Heading east from here you intersect with Los Caballos
trail and shortly thereafter, you'll cross the lake (if the water level is high) on a small dam. After you leave the lakeshore, the trail has great views across the Cuyamaca Meadow. A section of the singletrack continues across the paved access road to Los Vaqueros Group Horse Campground.
Much of the section between Hwy 79 and the horse campground passes beneath forest recovering from the massive 2003 Cedar Fire offering intermittent shade.
The portion of the trail west of CA79 seems to get much less use. I found it overgrown in places and much of it is very close to the highway. As shown here from the beginning, there is a steep little climb and descent at the start (at the shared driveway for some vacation rentals).