You don't get a "boarding time", you get a "port arrival time" or PAT. The earlier your PAT, the earlier your boarding group is. You will get a boarding group number when you check in at the port. Boarding generally begins around 11:15-11:30. My experience was that Cabanas was open for lunch earlier than noon. I think I made it up there around 11:40 and they were already serving. I'm not sure if Enchanted Garden will start serving before noon or not.