Lots of trails, but lots of open desert riding also. My avatar was actually taken there. I'll look around for some pics to give you an idea.
There's a couple dunes that aren't really that tall (200ft) and a bunch of sand riding, but there's also a lot of dirt around the West end of the dunes. I guess it's just pick a line and go. You really need to be careful of other riders on busy days. Most of the regular days you have to yourself, though.
I found a couple pretty gnarly dune jumps the last time I went, but wasn't on my bike so I look forward to airing out next time I go.