Yep, there's a fairly well-defined sign that must be posted to inform CHL holders of the "51%" status of the facility or the CHL holder can not be held responsible for entering it.
http://www.statutes.legis.state.tx.us/Docs/PE/htm/PE.46.htm#46.035
Sec. 46.035. UNLAWFUL CARRYING OF HANDGUN BY LICENSE HOLDER.
...
(b) A license holder commits an offense if the license holder intentionally, knowingly, or recklessly carries a handgun under the authority of Subchapter H, Chapter 411, Government Code, regardless of whether the handgun is concealed, on or about the license holder's person: (1) on the premises of a business that has a permit or license issued under Chapter 25, 28, 32, 69, or 74, Alcoholic Beverage Code, if the business derives 51 percent or more of its income from the sale or service of alcoholic beverages for on-premises consumption, as determined by the Texas Alcoholic Beverage Commission under Section 104.06, Alcoholic Beverage Code;
...
(k) It is a defense to prosecution under Subsection (b)(1) that the actor was not given effective notice under Section 411.204, Government Code.
http://www.statutes.legis.state.tx.us/Docs/GV/htm/GV.411.htm
Sec. 411.204. NOTICE REQUIRED ON CERTAIN PREMISES. (a) A business that has a permit or license issued under Chapter 25, 28, 32, 69, or 74, Alcoholic Beverage Code, and that derives 51 percent or more of its income from the sale of alcoholic beverages for on-premises consumption as determined by the Texas Alcoholic Beverage Commission under Section 104.06, Alcoholic Beverage Code, shall prominently display at each entrance to the business premises a sign that complies with the requirements of Subsection (c).
...
(c) The sign required under Subsections (a) and (b)
must give notice in both English and Spanish that it is unlawful for a person licensed under this subchapter to carry a handgun on the premises. The sign must appear in contrasting colors with block letters at least one inch in height and must include on its face the number "51" printed in solid red at least five inches in height. The sign shall be displayed in a conspicuous manner clearly visible to the public.