Wow, now I'm bummed about my hotel room.
Crap.
Don't be bummed!!!!
If you've booked a Disney View it won't just be of the bus terminal- I've stayed here several times, you can see the whole of Downtown Disney AND Disney World- Fireworks at night and the Epcot ball is quite clear! MK fireworks are in the distance but definitely still a visible show! If you want to propose on the balcony then I'd wait till at night time, it can look very pretty with all the lights, and then of course the fireworks.
Definitely request a high floor though, the higher the better. We've stayed on the 17th floor once and the 16th floor twice. Here was our view last time from the 16th floor:
Looking out towards Epcot:
To the right way in the back, those little buildings are the Contemporary and the BLT, that's where you see the MK fireworks- honestly though it looks further away in pics
Zoomed out a bit with the camera to show Epcot and the Boardwalk Area, in front SSR.
To the left of our view, Downtown Disney. NOT just the parking lot!!
And the sunsets are pretty nice
So again, don't be bummed! Make sure you tell the staff your plans- maybe they can make sure you are on a high floor? And if you are in Disney, yes you still could propose in the parks! Have a good trip