Any chance of setting up a web cam to catch them in the act? If you can post a sign in your garden that says that the garden is monitored 24/7 and that anyone who takes from the garden will have their photo posted on all telephone polls in the area as well as on facebook.
Your not going to find anything nasty enough for them to stop. But your going to have to do the flyer thing at least once before they believe you.
Welcome to BYC!
I would have to buy a camera for it. I was thinking of planting berries... black berries and stuff. But then the corn thing i thought would be kinda funny because they'd be eating it and that stuff tastes so gross.
the majority of my planting area is out in front. But this year i plan to only plant the good stuff in the back yard. going to get a lot of large pots, or totes to use as pots for tomatoes and peppers.