I agree with joe, and I'm sure the folks at the campgrounds will allow you to camp after you tell them what you're up to. Like stated above, apparently if you're under 18 you're going to be rowdy, but you can show them that it's not the case.
hopefully things work out positively for you. And if all else fails with the campgrounds, you can always ask to pitch your tent in someones yard, or in the trees next to the road.
have fun
-aaron