I could see the fireworks very clearly from my DVC balcony.
I was in a standard view studio and requested high floor level, which was given.
Some of the Villas face the other way, with the monorail right in front and the Poly on the left. (But that might be pretty cool)
Two years ago we had a two bedroom standard view DVC room that overlooked the waterfall right outside the back entrance on the fifth floor. We had a lovely view of the pool and the entire resort. We could clearly see the MK fireworks. Last year we had a two bedroom lake view room in the wing closest to the Polynesian. I actually preferred the standard view better.