I didn't bother to read replies yet, but I can tell you straight up that this shouldn't even be an issue. You don't talk about it, they don't know. Mums the word.
Don't post any signs about it. The reason liberals freak out about guns is that they think that no one should or does carry one. It doesn't occur to them to think that "normal" people around them might be carrying since only scary criminals and big, strong police carry guns. As long as you don't post a sign stating "Firearms are welcome here", I doubt anyone will ever think of it.