How Can I Keep Snakes Off My Property?

I live in South Mississippi, have a privacy-fenced backyard w/ 2 dogs in it that I want to protect. Also two rattlesnakes and a copperhead have come into our garage or right up to the garage in the past year. They lay in the walkways to our door, too. We have a corn field w/i close proximity of our house, and when we moved in had mice in the garage (that are gone now) so that used to be the problem. Not anymore though. The only natural predator of snakes that would be remotely reasonable to adopt is a cat. Our dogs do not get along with cats, and I don’t know if keeping a cat inside and letting it roam the front yard would be safe for the cat… does anyone know if adult cats have sense enough to not jump a 6 ft. wooden privacy fence into a backyard w/ large dogs? We’ve had one back there before that they chased up a tree. We just don’t know what to do and we want the snakes to stay away! I thought that snakes were afraid of humans, so why are they coming right up to our house?