This one is tricky. Boils down to express/implied consent. As Hawaii has it, it is assumed that property owners DON'T want guns on their property. Not really a bad assumption and not really a serious 2A infraction. Gun advocates want it the other way around; assume it's okay to bring a gun unless told not to.
I would prefer the first option. OTOH, it's not a real hardship for the property owner to post his/her desires. Call it a small fish.