Cabins open up at 1:30pm on the dot.... and, sadly, not a minute before. They have a rope up to the entry ways once you get off the elevators on each deck so that you can't even go down the hallways to see where your room is or if they are finished working on it.
Cabanas is open until this time (Maybe until 2pm?) As well as one of the main dining rooms. The main dining room is nice because it isn't as crowded, but then again, you don't get the view of the water around you.