There is a group of us that ride Bear Valley pretty religiously. The trails you mentioned....Cape Horn, Bee Gulch, Granite Slabs, South Lake Alpine are unbelievable. Some of the other really good trails are Illusive, Lodgepole, Upper and Lower Rings, Upper and Lower Tamarack are just as good, if not better. For a good climbing/downhill route...I recommend climbing from the Adventure Store up to the top of Cape Horn via Bear Valley/Alpine Trail, Bee Gulch, and then Cape Horn. Come back down and cross the Highway at the bottom of South Lake Alpine over to Lodgepole, which is located off the entrance road into the Bear Valley Ski Resort. Lodgepole will drop you into Granite Slab, which will drop you into the Adventure Store Parking Lot. If shuttling is your thing, you can ride from the top of Cape Horn all the way to Uttica or Spicer Reservoir. It gets pretty technical on the Slick Rock Trail, which is heavily used for 4x4 enthusiasts.
Talk to Jody at the Adventure Store. Super cool guy and he may fill you in on some "secret" trails.
Bear Valley = hidden mountain bike gem of the Sierras.