Where I am in Texas you cannot carry in any form at a place that is licensed to sell alcohol and gets more than half it's income from alcohol (i.e. a bar). You also can't carry while intoxicated unless on private property. I suppose there's no reason you couldn't go to an alcohol-serving restaurant that is primarily food, but I'd stick to coffee and not leave an opportunity for intoxication.

Of course I have no idea about Idaho specifically. Some of the states around me are similar but a few require a license.