There are about 30 sites if you include Cottonwood Pass, Cottonwood Lakes and the Equestrian site, which cost more.
I've been going up there for about 7 years and I have yet to be shut out, close a couple of times. However, I've seen people camped in locations which are not campsites. Let's put it this way the forest service isn't real active in the area.
To assure a site on a Friday be up there by 5 PM, it does fill up with late arrivals.
Bill