I used to live in Oregon, and rode a lot at the Central Oregon Recreation Area near Chemult; lots of great, fast woods trails, sandy roads, hills. Don't know if it's still open. China Hat is great for desert riding.
Also, there were a ton of tight, technical woods trails at Shotgun Creek near Springfield. The land was owned by a timber company that permitted off-road riding.
Check out the coast dunes at Florence and Winchester Bay. And the greatest woods riding in the world is in the Trask Mountains near Yamhill.