Put out a live cat trap, trap the cats and take to humane society. The owners will need to pay boarding fees, plus all updated vaccines, and a fine to get the cat back. After several cats or several fines they will get the idea.
I would have gone this route before the police but that is me.
I do understand your anger, that cat pee will never be out of your seats as the uric acid will soak into the foam pad, just wait for a hot humid day, you will smell it !!!!
-I'm Slyder and I suffer from "Gummer Syndrome"