I assume you would saddle him to go out in the open, right? Riding bare back is fun, but it takes ALOT of practice, and riding him this soon out in the open field, bareback, is a recipe for disaster, in my humble opinion!
You've gotten excellent advice. Stay close to the barn, corral, or to other horses he knows. Don't venture too far out, and always tell someone when/where you will be going.
Good luck, and have fun!