The fall colors will be very nice in early October. 108 (Sonora Pass) is one of CA's most scenic highways and has a number of spots to camp at. Many of the campgrounds in Yosemite's higher country along highway 120 (Tioga Pass) close around Oct-15th. Seems the CG's on Sonora pass stay open a bit longer and at least one is open until snow closes the pass. Mind you weather can close off either of those passes at any time for short periods. The east side of the Sierra's has several spots to camp at and many of the forest service roads are Sprinter friendly during reasonable weather. I think the timing might be close for some spots and then there are the hunters who will be all over the place. As mentioned the local fires are causing a mess right now but hopefully will be suppressed by the time you make it out this way.
I'll let those more familiar with the Tahoe zone comment on that area...lots of great places up in that area as well.
Virginia Lakes area is nice.
http://www.hikingwalking.com/destinatio ... inia_lakes
Trumbull lake CG would probably be closed but the fall colors are something if you hit it at the right time of the year. Nice drive.
http://www.fs.usda.gov/wps/portal/fsint ... Campground
Green Creek road is nice and there are several areas to boon dock at but you'll be in in the mix of hunters who swarm the area.
http://www.fs.usda.gov/recarea/htnf/rec ... ecid=65296
I've posted several spots in my area that are worth looking at and says whether 4x4/high clearance is required. The mono lake area is quite nice that time of year.
Hopefully you'll connect with somebody in an area you want to visit. I might even be in the area.