Okay, so your point is that your place of employment is open to the public and has no posting. Got that, and it is a good point. If you have employee only areas (break room, lockers, office space, whatever), though, that would seem to fall under 018.010 which has no "conspicuous" requirement, and would be covered by, say, a printed or spoken no-weapons policy.
My guess is that 018.010 is intended to cover employees but 018.03A is supposed to cover customers/the public.
And, of course, IANAL.