I had a longer post with with details of what I'm about to say but firefox is not being cooperative right now so heres the short answer:
It doesn't matter if MOA posts or not, one there isn't a penally for walking past a sign in MN, two MOA is a landlord and they can't deny access for tenants or guests.
On point one, if you are asked to leave a place that can deny you and you don't it is a max of a $25 for the first offense, but if they don't see it they won't ask you to leave.
On two, that interpretation hasen't been tested in court and the malls will kick you out, it might not be legal but it is SOP.
No it doesn't help, Go Vikings, and take the Twins with you.
BCA site that has mostly correct info on MN's carry laws:
carry in state buildings and courthouses