We have a female American Bulldog along with 2 other pits (male and female) as well as a group of cats.
Everyone gets along just fine. Oddly enough, we were looking for our female dogs to fight, but it was the lady bulldog and my male pit who got crossed (twice). They play HARD almost all the time, but twice under similar circumstances they got a little past playful with each other barking, growling, and looking like a fight. After breaking them up, however, there were no marks, ripped fur, or any real damage, and in a "real" fight between those two, there SHOULD have been. It was a great "show", though.
With regards to temperment, this is what I've seen so far and understand for the future. As pups, they can be REALLY headstrong (ours was). In our first week, she was openly rebellious growling if we scolded her and even nipping at us. Gotta' love bullies.
After a week of "we're the alpha here" treatment, she got out of that rebellious behavior completely. After a month, she was very trainable on basics (about 5 months of age). Now, feh, she's on par with any dog her age or even a bit older that we have. We figure she's going to be a star, and she's at boarding school for prep-training for other work.
As for as "home protection" goes, they're only as good as they're trained to be. The problem with using just an "instinct" dog i.e. a dog that just barks when he thinks he needs to, is that they may OR MAY NOT actually protect you. And they COULD protect you against family and friends.
To me, a "home protection" dog has one job and one job only: tell me if someone is trying to break into my home. I need as much time as I can to prepare for the intruder as possible. Having my dog get shot trying to protect me is nice and all, but I'd rather my dog bark his fool head off and then dive for cover when I or my wife start shooting.
With regards to home protection, a big dog is nice, but an armed owner is far more effective regardless of size.
For home protection, I suggest 3 min-pins. They eat less and are far more likely to alert to an intruder quickly. Also, while you might can hurt one of them on the way in, it's unlikely you get all three of them before they awaken the homeowner.
I'm sure other people have other opinions, and that's cool! I wouldn't trust ANY untrained dog, though, to have the sole duty of protecting me or my loved ones. To me, all a dog should do is deter a criminal, alert to a criminal, and, at best, slow him down long enough for me and/or my loved ones to bring arms to bear.
