Most campgrounds around there open between May 1st and some don't open until around July 1st. All depends on which ones you are looking for.
I'm in the same boat as you. The city life is really getting on my nerves, and I can't wait to get out in the hills. The problem is, most of the hills are covered in a couple feet of snow.
A good resource for campgrounds (in Nat'l forests is Forestcamping.com)
Have fun
Mike