I'm so glad you decided on the Grand Floridian.
This is from the Thread on the Grand Floridian:
http://disboards.com/showthread.php?t=513609&highlight=Grand+Floridian
What views are offered from the Garden View Guestrooms?
Garden View Guestrooms are available in Sago Cay, Conch Key, Boca Chica, and Big Pine Key. In Sago Cay, Garden View Guestrooms either have a monorail/water view, or a view of the resorts marina. Guests staying in a Garden View Guestroom in Conch Key would have a view of the resorts marina, or the gardens off of the quiet pool. Boca Chicas Garden View Guestrooms have either a view of the quiet pool or an obstructed view of the Seven Seas Lagoon and the Magic Kingdom Park. Big Pine Keys Garden View Guestrooms feature views of the quiet pool.
*We stayed in Conch Key and actually ended up with somewhat of a lagoon view and a view of the courtyard. It was fantastic
What are dormer rooms?Dormer rooms are located on the top floors of the buildings, and have vaulted ceilings. These rooms are smaller, but appear larger because of the high ceiling. These rooms have either two queen beds, or one king bed and sofa
*We had a dormer room and loved it!
I hear that there are different themes that the rooms are decorated in. Which theme is where?
Main Building
Most rooms are decorated in Cameo.
Two concierge rooms are decorated in Historic.
All Honeymoon Rooms are decorated in Floral.
Sago Cay
All rooms are decorated in Swan.
Sugar Loaf Key
All rooms are decorated in Cameo.
Conch Key
All rooms are decorated in Alice.
Boca Chica
Most rooms are decorated in Floral.
Two Garden View rooms are decorated in Historic.
One Lagoon View room is decorated in Historic.
Big Pine Key
All rooms are decorated in Alice.

Here is a link to a map of the resort:
http://www.kingdom-travel.com/Walt_...ian_Resort_Spa/Disney_Grand_Floridian_Map.pdf
When you've decided on what to request, call the Central Reservations Office and ask them to please write your request on your reservation.