If it doesn't have purple fence posts and "Posted No Trespassing" signs all over it, it ain't private in this state.
Not true. In order to arrest someone for trespassing, they must be given a written or verbal warning. Signs make sense when the property isn't visited on a regular basis by customers. It would be pretty stupid to build a parking lot and then put signs up all over the place telling people to stay away.
AtomSmasher is right. This is how they enforce skateboarding rules, etc... The owner can give an offender a verbal warning and if the person doesn't comply, he can have them arrested for trespassing.
Why do you think companies like Home Depot and Wal-mart have been sued (and lost) when someone gets hurt/mugged/robbed/raped in a parking lot? It's because the own the land. It isn't public property. Its private property with public access granted to the public for certain uses. By your logic, the inside of the Home Depot is public land as well since there are no signs and you are allowed to come and go as you please.
Texas Penal Code 30.05:
A person commits criminal trespass if he enters or remains on or in property or in a building of another without effective consent and he had notice that entry was forbidden or received notice to depart but failed to do so. To further explain the statute, the term “notice” needs clarification. There are several methods of notice that are acceptable under Texas Penal Code Section 30.05 (b)(2): •
Oral or written communication by the owner or by someone with authority to act for the owner. • Fencing or other enclosure that is obviously designed to exclude intruders. • A sign or signs posted on the property or at the entrance to the building placed so that it would be reasonably likely to come to the attention of the intruders, stating that entry is forbidden. • The placement of identifying purple paint marks on trees or posts on the property, provided that the marks are: 1. Vertical lines of not less than eight inches in length and not less than one inch in width, 2. Placed so that the bottom of the mark is not less than three feet from the ground or more than five feet from the ground, and 3. Placed at locations that are readily visible to any person approaching the property and no more than 100 feet apart on forestland or 1000 feet apart on land other than forestland.