It's usually a good idea for anybody to disclose their autism or almost any other disability that's not "physical" in the US. Especially when your job doesn't involve computers, teaching, or perhaps an office job.
It's an unfortunate fact that pizza delivery drivers are considered "a dime a dozen." Many bosses who are not enlightened, or don't have kids with autism, would probably think of a reason to fire him the first time he "messes up" after he discloses. I hope this boss is one of those who doesn't know the "employment-at-will" laws.