If there's no sign telling you that you can't camp there, you should be able to camp. Just remember to be respectful in a National Forest and don't leave a trace of you being there. Always remember the rule to leave the spot better than you found it so that people can continue to camp there for free in the future.  Don't block any road entrances etc either when you're trying to find a place to camp. The more that you can stay out of the way, the better.