For a while, they were only taking ADRs for the first hour it was open, but I believe they are now taking ADRs all day again as I made one for around 4pm for my next trip. It's a very small place, so I would recommend an ADR if you want to eat there. I have had better luck doing a walk up at Skipper Canteen than at the Plaza, especially since they updated the Plaza menu to include items other than sandwiches. I think when the menu was primarily sandwiches, people on the dining plan felt they weren't getting the best value there. Now that they have some regular meals as well, that isn't as much of an issue and more DDP guests are willing to use credits there.