Greer Ranch (a.k.a. The Nursery or The Farm) is a well built series downhill trails that offers some easy access and easy climbing for redonkulous descending mountain bike action. The trails have awesome berms and jumps with the bonus of the hospital only a stone's throw away. You can stack several loops for really fun riding in this area. There is some good signage on the trails, with wicked artwork for the trail name signs. There is no signage at the trailhead though. Simply ride up the road from the parking and you can access the trails off of that road.
The 215 Enduro Trail is featured here as a building block original downhill trail in the system. The Electrify Trail climb can be used to get to the top and ride 215 Enduro or Monk Dawg. See how all the trails fit together on the Enteractive Map. The other linchpin descents are Distortion, Insidious, and Revolution which can be accessed on the other side of the road. The whole area makes for some great session riding and loop stacking.
Access the trails by parking at the south end of Scenic View Drive, which is a dead end road right beside The 215 freeway.