The best place to start looking for organized events in California is http://www.cal4wheel.com/
. They have a list of California clubs that sponsor events and such.
As to Glamis at Thanksgiving.... It's all about horsepower and alcohol. We used to go and take the sand toys when we had them, but it got too crazy. I can't personally see having any fun out there in a Jeep, nothing but sand dunes. But if that's your thing, go for it.