yeah ok.. so I ride sand bikes too.. TRX250R, CR250 to name my favs.. Anyhow, I make a pilgrimage to Glamis a coupla times a year, from Seattle.. it's a bit of a drive, but WAY worth it..
I cant plan stuff out too far ahead, but I'm willing to hit the dunes just about anytime..
Might also want to try out the Oregon coast in the summer, when it's too hot to ride Glamis, or if you want to see the tallest, steepest dunes in the country, try out St Anthony, ID
check out glamisonline, sandbros.com, mudsand.com to name a few..
BTW.. SandFest on the Oregon coast, at Winchester Bay, in August, is the closest thing I've seen to Glamis on a 3 day weekend, without all the drama and cops, and jail time.. Same naked college girls tho