You might try a simple sling shot and arsenal of rocks or bb's. A little sting in the behind might discourage the dogs from your yard. I used this tactic on a yappy little sheltie who was confused about where his turf ended and mine began.
Hopefully you've also had a conversation with the owner - communication is often key. Calmly let them know about the damage being done, and ask the neighbor what might be a good solution. Perhaps bring a gift plant to the conversation as a show of good will. As others have noted, a neighbor-war is never pretty.
