It is sad that a landowner can be sued when a trespasser, without permission, invades his property and gets hurt. However, although it is true that it can happen, the installation of fencing, and signs; can help you in court. If you took "reasonable efforts" to keep trespassers out, you will have a better defense than if you did nothing.
It depends on the court, the judge, and the circumstance. But often, in the cases that I have heard of, when a landowner had fences and signs, that was in HIS favor. Locked gates were, in the cases that I have heard, the biggest thing in the landowners favor. If the gate is locked, and a trespasser crawls over it; that trespasser took steps to overcome the "reasonable efforts" the landowner had taken to keep people out.
From my limited experience, that was the biggest factor in limiting liability. (at least here in Texas)
