I use my cams on public land and have not had any problems.I dont think anyone has ever found them though.I use cable lock to lock mine down but It is more to keep it firmly attached to the tree.
I set mine about 5 feet off the ground and make sure it is straight and no branches in front of it.I also like to put mine pointing up a trail and then you will always get a pic of the animal coming or going on the trail.
I always set up,make sure it is on and then I walk from all diffrent angles on the trail and make sure it is working.I hunch over and pretend to be an animal.After I take 5 or 6 then i check the pics to see how they are.This will tell you if the cam is staight and if you need to move it up and down on the tree.Sucks to get pics of elk or deer with there horns cut off.
I hope your cams are tough because mine have been used as rubbing posts for bears,chew toys for deer and elk and a comfy spot for squirrels to poop on.
Here are a couple of mine ..
Here is one of the chewers..
This next one was a great surprise as I hadn't seen this buck before.I decided to let him grow for one more as he was still a little young