If I and nine other people own a restaurant, may we post a sign saying, "No guns allowed" and prohibit you from entering if you have one?
Sure, it just won't mean anything. Now if you could find nine people stupid enough to be partners with you and y'all were sissies and scared of armed citizens then in Texas you would have to follow the provision below.
If you did post it properly, which I have never seen performed I and about 100 million of my best friends would not patronize you business.
PC §30.06. TRESPASS BY HOLDER OF LICENSE TO CARRY CONCEALED HANDGUN. (a) A license holder commits an offense if the license holder: (1) carries a handgun under the authority of Subchapter H, Chapter 411, Government Code, on property of another without effective consent; and (2) received notice that: TEXAS CONCEALED HANDGUN LAWS PC §42.01 31 (A) entry on the property by a license holder with a concealed handgun was forbidden; or (B) remaining on the property with a concealed handgun was forbidden and failed to depart. (b) For purposes of this section, a person receives notice if the owner of the property or someone with apparent authority to act for the owner provides notice to the person by oral or written communication. (c) In this section: (1) "Entry" has the meaning assigned by Section 30.05(b). (2) "License holder" has the meaning assigned by Section 46.035(f). (3) "Written communication" means: (A) a card or other document on which is written language identical to the following: "Pursuant to Section 30.06, Penal Code (trespass by holder of license to carry a concealed handgun), a person licensed under Subchapter H, Chapter 411, Government Code (concealed handgun law), may not enter this property with a concealed handgun"; or (B) a sign posted on the property that: (i) includes the language described by Paragraph (A) in both English and Spanish; (ii) appears in contrasting colors with block letters at least one inch in height; and (iii) is displayed in a conspicuous manner clearly visible to the public. (d) An offense under this section is a Class A misdemeanor. (e) It is an exception to the application of this section that the property on which the license holder carries a handgun is owned or leased by a governmental entity and is not a premises or other place on which the license holder is prohibited.
http://www.txdps.state.tx.us/ftp/forms/ls-16.pdf