X2 for Christmas Valley. There is a big event on private property there this Memorial Day, its advertised in Craigslist. Sky is going over there for something Memorial day, I know a bunch of people run Schwartz Canyon every memorial day too.
Also I saw pics of NW Mogfest, and it looked cool, but I didn't see anything challenging there.
Dunes? I live in Eugene. The dunes get old.