Cats hate oranges, so see if you can make or buy something with a heavy concentration of oranges in it and spray it in all their favorite areas. If worse comes to worse, get some cat traps from the local shelter and catch them and turn them in. It’s probably a death sentence, but when you don’t have a choice...
Chinese restaurant, puleeze. ;-)
It's a tragedy that these creatures were left to fend for themselves in the first place. Diseases, bloody fights, ticks, fleas, unfettered reproduction, exposure to bad weather, unreliable food or clean water available...all that because some people just wont be bothered to take care of their own pets. If these are your neighbour's pets, you should let him/her know that you will be trapping them and taking them to the pound for their own welfare. Even if they are put down and not adopted out, they will be better cared for.
Please don't shoot them or hurt them! They would more than likely love to have a warm, clean bed, good food and water and affection, but it was humans who released them in the first place. They are just trying to survive. Be kind!