A cat run is the best option if owners want to allow their cats outside. I have 3 cats,and will build a run for them.It is safer for them,and it is nicer for the neighbors. There are some really great runs that have been built that will give you ideas.
If I catch cats on my property I remove them so they are no longer a problem.I will not waste time and money on deterents,or taking the cats to their owners(if I know them).Roaming cats have a much higher death rate.It is spring here and the dominant smell is cat pee. Time to put out the traps.
Some runs:
http://www.catsofaustralia.com/cat-enclosures.htm
Just for cats sells a booklet to build a run:
http://www.just4cats.com/
Keeping what is yours on your own property makes for better neighborhood relations.If your neighbor has animals that tresspass they need to remedy the situation,or accept the results that happen with roaming pets.My neighbor paid over $400 after their husky came into my yard and bit up my dog.