I agree with getting a caretaker that you trust, and check with Fish and Game and the Sheriff and see if he can also be your "agent" which means the caretaker is calling them if there are trespassers and prosecuting. Without teeth, the authorities won't do a thing.
As others have pointed out, it helps to be known as someone that is a bit off, and target practicing on the property will only help your side of things.
But, the flip side of the coin is that if the offer for the property is good, maybe another, better property can be found.
