From time to time I have encountered dogs and owners as you describe. Our local chief of police once wrote about the problems of dogs and their owners in our city newsletter. (City has fairly well enforced lease laws.)

This guy already knows he has to keep his dogs fenced in or he is in big trouble. Make sure you know his name and address, and be sure he knows you know it. Check with local law enforcement(informally if possible, you may get a better discussion) to see if there have been any problems with this guy.

If there have been no problems with this guys dogs escaping, I would use the alley when you need to and warn sparkle to stay back from the fence.