From Hwy 35 at Black Rd. proceed north on Hwy 35. On the right hand side of the road will be parking at Sunnyvale Mountain. The trailhead is on the northern side of the parking lot.
The main trail is a combination of old logging road and singletrack. Follow the ridgetop as the trail winds among various hills and dales. Here you'll encounter some climbing, but mostly a very nice beginner trail. Some of the climbing can be a bit much for beginners, but it's all walkable and certainly not too long.
Skyline makes for a very nice out and back, riding from parking lot to parking lot. Most of the time you feel quite far away from the highway, deep in the trees.
For its duration you'll experience gorgeous views of the Santa Clara Valley and sandstone rock formations.