I assume your question pertains to Maine law?
If so, no, Maine law does not *in general* prohibit you from carrying a concealed firearm into an establishment licensed for on-premises consumption of liquor. The exception being that if such an establishment has posted a notice prohibiting or restricting the possession of firearms in a manner reasonably likely to come to the attention of patrons, then carrying a firearm is a crime.
So, bottom line: No sign, you can carry.