Idon't recomend shooting the dogs! Loose dogs are the owners fault, not the animals anyway! I lost a good lease due to someone shooting the neighbors dogs once, and it could put you on the wrong side of the law.
Check on any laws concerning loose animals, but if its in the country, there might not be any helpful laws!
As others have said, you might try trapping them and bringing them back to the owner! (that may work, show them that you don't want to hurt their dogs. Then if they are jerks it won't help at all bringing them home!)
Trapping them and painting them might be the answer! Or even spray them good with some skunk scent, maybe the owners will keep 'em home after that! Good luck with a tough situation!