It really depends on where you'd like to be on property. Sago Cay is probably the closest to the main building, monorail & bus station. I would guess a 2 minute walk to the pools and beach. Garden views here can be of the monorail going by, or you can ask for marina (which is also considered garden). This is a very quiet building. Conch Key is another quiet location, with beautiful courtyard garden views. This building is closest to the boat dock, but furthest from the main building and pools. Considering the size of the resort, by furthest, you're probably talking not more than a 5 minute walk. Big Pine Key and Boca Chica are centered right near the courtyard pool and garden room balconies might be a bit noisier here. They both offer views of the interior courtyard garden and pool and are both within a minute or 2 of the main building.
All the standard garden view rooms are going to have balconies. The rooms on the top floor have smaller, enclosed baclonies. These are called dormer rooms, sleep 4 (over the age of 3) and come with cathederal ceilings. Corner rooms can offer you some extra space and 2 balconies.
I wouldn't suggest that you request a certain room number or get too specific, instead just list (by priority) what you would like. You can also ask again at check-in. The CM's can usually go through the current inventory and let you have a choice of what's available in your category.
Tammi