Have you tried talking to your neighbor(s) about their cats?
I live in a very animal friendly neighborhood. Everyone has at least one dog, most more and many have at least one cat. Unfortunately, a few just let their cats run loose. When the one had kittens, she hid them behind some bags of mulch next to my house. My two neighbors give me a hard time for not calling the pound about them.
It's not like I'm a cat hater. I like their energy and the way they move. I had a siamese and a Maine coon, but they died of old age a few years ago and I've not replaced them. Since then, I've learned to see cats and cat people from a different point of view.
If you know of a way to keep them away, I'd be very interested. I've tried many things with no success and I'm ready to go to the next level.