Best advice, post the full perimeter of you property with the bright yellow POSTED signs. Every 75 feet or so should do, but I would put them even closer if you can. Place a few well hidden trail cameras to capture evidence and go from there.
Simple and to the point. In TX, it's required that the signs be 100' apart in timbered land and 1000' apart in open land. 75' sounds good to me. Also, according to the penal code, livestock fencing or purple paint is enforced as no trespassing notification. I would go with the signs.
