PLEASE don't call places and ask what their policy is.
If a place doesn't have signage or hasn't thought about the matter, you have just put the issue on their radar. Bad move. Most people/places are risk averse, and your call can put the matter front and center. Not good.
If a place does have signage/doesn't want guns, you have a) encouraged them to post/post more signage, and b) informed yourself rather than forcing them to inform you by "conspicuous" signage which you must "knowingly" ignore in order to (hopefully not) be sucessfully prosecuted.
It's much better to use your suave, debonair, and informed manner to deal with issues that may arise rather than bringing them up ahead of time.