Honestly, it is the neighbor's fault, but your problem. Being a pit bull owner, no matter what happens you will be to blame. Sorry, but that is just the way it is. :'(. You need to fix your fence and never let your dog out there, unless you are there. Just for good measure, you may want to use a leash on your own dogs in your own yard. If you call AC, they will somehow find out, and then will more than likely try to get even. That is just how people who let their dogs roam are. You may need to "rehome" their dog, if it keeps coming in your yard. Wait until it has been a long time, since you complained about the dog to anyone, before you do it. Believe it or not....but you do not have a lot of options. Other than completely securely fencing your area with privacy fence. Which may not be practical when renting. If that dog soemhow gets into your area and your dog mauls it....you are going to have nothing but problems from AC and your landlord. So not fair, but just how it is.