Leave the gun in your hotel room, if you have to. The simplest way to make it safe is to disassemble the gun and take the barrel (or cylinder) with you. Lock the rest of it in a briefcase or suitcase.

I wouldn't think it too wise to carry it into a convention center unless the locality/state you will be in has provision in their laws requiring you to be asked to leave and refused before you are in violation. If failing to heed posting is all it takes, don't risk it. It seems a lot more likely you will come to grief over a weapons violation than seriously harmed in a stick-up in an environment like that.