As a owner of pitbulls we also have a common fence area and we have trained our dogs that that area is off limits. I might also suggest that you talk to your neighbors about if they are close to the fence if you could spray them with a water hose and tell them no or putting up a privacy fence. All dogs no matter their breed will figure out how to get in a back yard. There are really no bad animals just bad owners that do not train their pets. Also you may want to consider getting a electrical wire to run on your fence area but check with local code enforcement first.

re: "no bad animals, just bad owners..."

I'm not fully convinced. In my town lately and several times during the year, in the news there have been reported incidences of pit bulls mauling or killing. I have to ask why the reports always mention pit bulls. You don't hear news about german shepherds, rotweillers or pomeranians hurting or killing anyone.