All bully breeds have the potential to develop dog aggression, no matter how they are raised. They may do great with other dogs until one day they just don't anymore. The saying goes "Never trust a pit bull not to fight", and I live by that. Even though my apbt gets along amazingly with my other dog, I take plenty of precautionary measures to keep the peace. They are never, ever, ever left alone unsupervised. Not even for five minutes. When no one is home to supervise, one is crated and there is a door between them. It may seem like overkill to someone who's never lived with bully breeds or dog aggressive dogs, but I just consider it precautionary.
Keep in mind that any of the bully breeds can "turn on" at any age. I've heard stories about bully breeds that have coexisted peacefully with other dogs for years and then one day, horrific dog fight.
I don't want to sound like an alarmist. Responsibly bred apbts/amstaffs are absolutely worth all the effort to me. They give sooo much, and are amazing companions. I just like to stress the importance of never being complacent about the fact that dog aggression *is* a breed trait. Crate/rotate is a very real possibility any time you bring one into your home with other pets. Is that something you can live with if necessary? I hope I never have to, but I'm aware that someday I may have to.
(Disclaimer - some lines are "colder" than others, and some are very hot. I would discuss it with the breeder you choose, but know that this also isn't a guarantee that you'll have a dog that gets along with other dogs.)