Rule 1 - Don't call and ask. Show up and if there is a sign on the door, either ignore it and if asked to leave then do so, or go some place else.
One problem with calling is that you may get someones opinion and not the policy. Every AutoZone I have been to is carry friendly, just not for employees. Starbucks policy is to follow local law even though they prefer you not carry in the store but they don't post gunbuster signs. Another problem is you point out the lack of signage to someone who may complain to management and then the next thing you know, they put signs on the door. So a place that has not been posted in the past now becomes posted.
"For these reasons, today we are respectfully requesting that customers no longer bring firearms into our stores or outdoor seating areaseven in states where open carry is permittedunless they are authorized law enforcement personnel."
http://www.starbucks.com/blog/an-op...-schultz-ceo-of-starbucks-coffee-company/1268
Why would you want to patronize an establishment that's anti-2a anyway, signage or not?