As noted, it depends on your state laws. I'd suggest starting here: http://www.handgunlaw.us/
In Arkansas, I almost never see a "no firearms" sign. When I first started carrying, I expected to see them at banks, but never have.
A gunfight is not the time to learn new skills.
If you ever have a real need for more than a couple of magazines, your problem is not a shortage of magazines. It's a shortage of people on your side of the argument. -- Art Eatman