How to keep dogs out your yard

http://www.havahart.com/articles/keep-dogs-off-lawn

Fence

Put up a fence.

Spread hot pepper flakes around the perimeter and replenish as necessary.

I had the same problem and since the owners would not keep the dog contained after asking nicely, I ended up catching the dog (friendly, no tags) and taking it to the pound. The owners had a half hour drive each way and had to pay to get their dog back. It was an expensive lesson, but I was desperate. I hated that the dog liked to use my yard as it's bathroom. It's interesting that the owners kept their dog on a run after that.

Check with your state laws. In our state it is illegal to allow your dog off leash, except on your property. Do not put hit pepper flakes out, that is cruel, snd it isn"t the dogs fault it is the owner. Also in our state it is illegal to put a dog on a chain. Continue to call animal control, if that doesn't work, take the owners to court. After they pay a few fines maybe they will learn. Maybe they should not be dog owners.

Check what your city's regulations are for free-roaming dogs, most don't allow this.