there'd be one if "every coffee shop" Get real. Oh, I forget, that's what you do, exaggerate every situation.
But now if there were, do you really think someone would be dumb enough to pull a gun? Hell, that'd be the safest place around. Use some common sense will ya. If I were a thief, which house would I want to rob, the one that I knw had weapons or the one that I knew didn't. Don't strain your brain on this.