www.capitol.state.tx.us/statutes/pe/pe0003000.html#pe006.30.06Above is the link to the relevent section of Texas CHL law, section 30.06.
While I'm not lawyer, it would seem that in order to be in violation of the law:
1. You carry a handgun
under the terms of your CHL onto someone's property who has not consented.
AND2. You have been given written or oral notice by someone in apparant authority that you are not allowed to carry there.
OR Upon having notice, you fail to leave.
What this means:
If you had not been told that it was illegal, you could carry a handgun in the parking lot. It only becomes illegal if they tell you to leave and you don't.
As for having the handgun locked in the car in the trunk, it would appear that that is perfectly legal, as long as you have not been given notice otherwise. It would appear that the 30.06 sign is not effective notice, as that law states that it is illegal to carry the gun
under your CHL. Having a gun in the trunk of your car has nothing to do with a CHL, so therefore the 30.06 sign does not apply.