Our two are mainly indoor cats and they use our garden as a toilet. I hope they don't use anyone elses and the speed at which they go out and come back leads me to believe they stay in our perimiter.

However, for some reason, the two party girls seem to have attracted a following of all the local waifs and strays from all around the neigbourhood. They are both doctored so it ain't that. It is very difficult to put strays off while trying to keep ours in in the garden but water seems to be most effective - A hose pipe definitely does it!

If you don't have your own cats how about some sort of garden sprayer triggered by movement?

MP