i was in almost the same situation earlier this year! our old neighbors had a sheltie and a black three-legged dog that they would just let out of the fence. they have a fence to put them in!they just don't like keeping them in there. they say it's mean to keep them locked up. the worst part is the dogs would run straight into our yard and try to attack us and Beanie! one time the sheltie about had Beanie's neck when i threw a rock at it.....what else was there to do? he was gonna kill my baby!

REVENGE!-we called the police and the dogs came after them......needles to say the dogs didn't run around any more and the neighbors were no longer there if we needed to "borrow a cup of sugar".lol

hope your problem works out!