Oops, sorry to be cranky! My opinion is worth what you paid for it. One can reference the laws on the TX state site.
There has to be a proper 30.06 sign on the hospital entrances to prevent carry based on the sign. You don't have to get written permission.
My comment about the instructor was because in TX, extreme care and effort was put into designing the law and in its revisions to make the signs extremely well defined to avoid any doubt. I know a guy from the TX CHL instructors association and one thing folks wanted to accomplish with the revision was to get rid of those silly red circle line/gun signs and make any place that wanted to ban really put an explicit and ugly sign in front. My doctor's building has one and you can miss it. It is perfect.
Same argument went with churches.
Given carry is a life or death issue and also has legal penalties if you get it wrong - an instructor licensed by the state who has it so wrong is a threat to his or her students and the structure of CHL.
On the other hand, I should have explained it more.