I don't really care a whole lot about the signage laws. Unless there are metal detectors, all they can do is ask you to leave, if they see your weapon.
I bet if this poor father had been carrying, the bad guys would have run off the minute they saw his piece.
Ever since I moved out of Californistan, my thoughts have changed to the point where now if I can't carry, I don't really want to go there.
About the only inconvenience to date is that I can't go inside the Post Office. I am hoping for a change in that to come as an aftermath of Heller. For now, I just go into the private mailbox place that is closer than the Post Office.
That varies from state to state. In Texas, if they have the proper signage, and you get caught carrying there, you've committed a crime.
But most of them are too chickenshiite to post the humongous sign that is required. In fact many places which posted at first after the CHL law went into effect no longer do. Most of them in fact. (Not counting places off limits by law)