Some years ago, I had this problem. Only house in small close without a cat and everyone else's used my front lawn. Tried everything. Smelly deterrents of all sorts - from pet shop, mothballs, etc. eventually Jayes fluid to no avail. Then took up grass and laid shingle. Worse.
Then got a cat of my own. It saw off other cats and (because most cats don't) didn't use the lawn itself.
But. I believe the best solution is actually the sonic cat deterrents you can buy at garden centres.