Black Rock Desert
The Black Rock Desert in northwestern Nevada is pretty awesome. Check out Soldier Meadows Ranch ( more info on its web site). Just have to pay attention to the weather for any snow in the higher valleys or passes.
Riding in the southern part of Ca. probably is best this time of year. Also check out Tecopa Hot Springs area, China Ranch (the date farm), and Dumont Dunes.
My favorite ride is the one I'm about to start!
'06 Husky TE 610, '07 Triumph Tiger 1050, '93 ATK 605