You should be able to drive on it, or they should leave "a way out". I mean, what would happen in an emergency? Would you be expected to park 2 streets over and walk to your car if you were hurt or someone's wife went into labor?
Blacktop is usually safe to drive on after about 2-4 hours, but like someone said, don't go fast because some of the crap is still loose, and you don't want that being slung up.
You'll hear a lot of pebbles in your wheel wells, but no big problem. Even if some stick inside, they'll fall off soon enough. It's no big deal unless they JUST got done steaming it.