Here's something purely anecdotal: recently stayed in a motel in very rural Arkansas. In the morning, I noticed a Chevy Bolt (or similar) plugged in with an extension cord. Asked the clerk about it. She said it was a relatively rare situation but they didn't have a problem with someone using their outside outlet.

I suppose I can't extrapolate this situation to everyone, but I have a feeling if you provide your own cord, most motels won't have a problem with you charging. Especially since it'll be uncommon. If everyone had EVs, then they might start putting a fee on it.