Sago Cay overlooking the marina is beautiful, but you can also check on Boca Chica, high floor, overlooking Narcoossee's. The rooms in this area have a bonus feature of being able to see some of the MK through the trees.
The GF doesn't typically pre-assign rooms, they select from available inventory when you arrive. My suggestion, is to try and get there early (before noon) and and repeat your requests to the check in CM. Chances are your room won't be ready, but you can take care of the pre-check in and have a higher number of rooms to choose from. For an added bonus, ask about a corner room there as well. Some of them have extra floor space and a 2nd balcony with a nice view.