Can you use a dog whistle on your neighbors dog?

Yes you can use a dog whistle. But, what is better is this thing called "bark off". It emits this extremely high pitched noise that people over 30 can't even hear. It will almost be like you are training your neighbor's dogs! Put it on a part of the fence that is closest to them, and turn it on once they start barking. Turn it off when they stop. Keep doing this for a while, and they will realize they hear an awful noise when they bark. It is humane, and they actually recommend it for keeping stray dogs away from you and your property. Hope this helps the incessant yapping!