Foresthill is a great place! All levels of trails - believe me! To get to Forresthill from I-80 heading North out of Sacramento, go toward Auburn, CA and take the Forresthill exit. Follow the exit and signs for about 17 miles. You will go through the small town of Forresthill and then turn left at the signs for the OHV area. Sugar Pine staging area is first. There's also overnight camping at a trailhead up further.
The trails are two-way and mostly easy-fun, but there are really challenging trails Trail 6 comes to mind. There are some black diamond and double blacks on that one.