We just went through something like this. Our neighbor had two pit bulls (a breed that we love, but unfortunately all to often fall into the wrong hands.. like our neighbors) that they didn't supervise. Both pits knew how to climb out of their fenced in yard, and liked to come over to our unfenced yard all the time. We have a small beagle who gets along famously with other dogs, but these two dogs have shown dog aggression towards her, so we had several discussions with the owners about please supervising their dogs outside, or finding a better solution to keeping them outside for hours on end.
My husband or I would always call our neighbors son to come get their dogs when they where in our yard, because I let my dog out on a leash several times a day to potty, as our yard is not fenced, and I, being 8 months pregnant, can not separate three dogs if need be. Two weekends ago the dogs got and came after my dog and I. I was not bitten, but the skin on my dogs neck was broken, and unfortunately to get the dogs of our dog, my husband had to resort to violence and use a baseball bat, and VERY sadly, one of the pits lost their life.
Our neighbors acted like they couldn't believe he would do such a thing, so WE called the police to make a police report because our neighbors kept screaming they were going to sue us and press charges. The officer that responded wrote them a ticket for violating leash laws and told my husband "had it been my pregnant wife, we'd be cleaning up two dead dogs instead of one."
It's sad, but leash laws are there for a reason. The unleashed dog's owners are ALWAYS at fault. Talk to your neighbors, and if the problem persists, contact animal control to file a complaint. It's better that the owners get ticketed and learn responsibility then to end up in a situation like our neighbors.