always make sure you return your neighours cats 'presents' back to where they came from - you're entitled to do so!
I appreciate that cats pooping in your garden is irritating as I have the same problem, but what good does returning it to the cats owner do except cause more bad feeling? It's not like a dog where the owner has control of where they go. My neighbour did this to me and it made me so depressed as I couldn't stop the cats without following them every time they went out. Please don't do this Ask the owner if they are okay with coming to clean it up; I would have done that willingly.
Spray them with water and peel oranges over your borders leaving the peel there. You have to repeat the process but it works. I have THE MOST DETERMINED cat who dispells the theory that your own cats don't go in your garden, I tried netting and he poo'd through the netting. I put loads of kebab skewers in the border and he perched of the edge of a 2 inch piece of wood hanging his arse over the border! But the oranges... no sir-ee bob, out and off to the wasteland instead!