Around here, animal control will at least make its presence known. (They've told us they dealt with owners, but that we'd have to gothrough the Freedom of Information Act to find out how; the dog that bit me was on a route I rarely have occasion to ride so I don't know if it's still out and about.)
I watched one of our guys stop a dog completely wiht a good squirt from the water bottle. I'm a camelbak girl for my own needs but I'm going to work on that skill.