Thanks all around for the information. The only neighbors on the alley are a car wash, a parking lot next to them, and another parking lot next to the house owned by a body shop that is delinquent on their taxes anyway. I might just be evil and put up the fences if this wasn't in a well-kept and well-known neighborhood.

My dad always used to say, "It's better to ask for permission than to beg for forgiveness." But the guy who is recommending I just put up the fences said, "It's better to ask for forgiveness than permission." I'll try to do it the legal way as long as I'm not on hold more than ten minutes when trying to call the city. [[I guess I better put in that order for fencing now...)