One place I remember specifically is at MGM near the stroller rental. It is not just a cart, but a permanent stand. We were buying sweet rolls, coffee, juice, etc. to eat for a quick breakfast snack and I was surprised that they didn't accept credit cards (or room key for that matter). There were a couple of other places, but this is the one I specifically remember. I just tried to look up my receipts that I save from year to year and I couldn't find the name of this stand.
I just didn't want you to be under the impression that all places with cash registers take credit and debit cards.