I am an expert in home self defense and security. I love guns and surveillance. I would suggest putting up a couple cameras in your yard with a feed that goes to a special tv you can monitor at all times. Buy a cheap motion detector, if anybody walks by, the alarm goes off. If you dont like guns you can always buy a cheap blank firing pistol -
http://www.maxarmory.com/ - anybody comes in you shoot at em, but you cant kill em, just make em shit their pants. Also some motion sensing floodlights and a sign that says trespassers will be shot. Cheap and extremely effective home defense.