By the way you stated "...unfortunately the road to get to the public land goes right through our property and we can't do anything about it.", sounds to me that is an official easement.
If that is the case, many people don't or will not know about it. Post both sides of the road on your property with No Trespassing signs. That should stop some traffic.
If this is a continuing concern, contact the DNR and set up a sting. While it's serious business, it is funny watching these guys get busted on video shooting at a fake deer!(whole mount)
iSnipe