Being that your closer to the PNW I would be inclined to look more north than south. Your 3+ hours from my area and I still need to drive 1.5 to 2.0 hours to reach a good riding area.
All the riding areas that I ride in are mostly in the mountians where red stickers are allowed. But, dust becomes an issue was we've had a very dry winter and spring. Two weeks ago Tony and I went to Elkins Flat to ride and it was hecka dusty...which brings down the fun factor...just a bit.
Not sure if you have ever checked out this site :
http://www.riderplanet-usa.com/atv/t...ornia_list.htm But this might be a good place to start.