Sensitive subject....but what should I do?????

This is an age old problem, but I really need some tips/advice.

First let me say, I love cats. Want to make that clear and up front. I don't have cats because my whole family is allergic to them. Now the topic.......

New neighbors across the street. Friendly friendly friendly guy. Walks his dogs daily and his cats too. Its funny you see the whole clan walking down the street. Anyway....his cats poo in my yard and pee on my car tires. They are outside cats. He lets his dogs poo on peoples yards, and he picks it up. Responsible pet owner.

But he I'm sure he doesn't know that his cats poo and pee in my yard. It is driving me absolutely positively insane. The smell, stepping it it....ugh. Its terrible. I have asked my DH several times on how do I approach this guy about it. I don't want to create trouble, and finding the exact words to broach this subject is difficult for me. He says live with it. Let it go, it's not worth getting hard feelings with a neighbor over. Want to keep the relationships on a good level...etc etc.

But I love my garden, I work hard on it and I just can't live with the poo!!!. DH doesn't garden. Won't step foot in the garden, so he does not really understand.

Our lot in front is narrow and triangular. I thought about putting in a motion sensored sprinker to deter the cats but then anyone walking on the sidewalk would get blasted, so that is out.

Maybe I just needed to vent. Well, whaddya say? I don't want to turn this into a dog vs. cat war or any kind of bash the cat thing. I just need advice - should I talk to the neighbor and risk the hurt feelings thing or let it go and live with it.