I'm not a lawyer, but I would expect your statement to be true. As a Texan, there are certain forms of behavior I expect in a public establishment; and (to the best of my knowledge) this is not arbitrarily enforced. If the rules are broken, it is incumbent upon the park to either eject the violator, or bring charges against him/her. To anything less would be to encourage this behavior and be seen as promoting it. Given the relatively large sum of capitol Six Flags invests in maintaining a safe and fun family orientated image; I would expect that your assumptions would be true.
Now, if only we could find a way to prosecute the homo event's sponsors for conspiracy to commit public lewdness...
Texas Penal Code
§ 43.23. OBSCENITY.
(c) A person commits an offense if, knowing its content and character, he:
(1) promotes or possesses with intent to promote any obscene material or obscene device; or
(2) produces, presents, or directs an obscene performance or participates in a portion thereof that is obscene or that contributes to its obscenity.
Texas law makes violation of the public lewdness statutes, of which an obscene public performance is, punishable as a "state jail felony" (just below 3rd degree)
Among the items defined in the lewdness statute as punishable, in general, "patently offensive" and "deviate" acts including specifically what is commonly called groping of the sexual organs and public forms of sodomy, which is indeed still illegal in Texas despite the supreme court's action against our other sodomy law. In short, Texas law technically authorizes the arrest and felony prosecution of a wide range of lewd and obscene activities that happen openly and regularly at most homosexual "pride" events and that, given their history at other theme parks, will likely occur at Six Flags as well.