Many guests gather on the bridge between the BW & International Gateway to watch the upper fireworks from Illuminations - though if you have a BW view room, you usually get a better view from your balcony
You can see some of the HS fireworks from the pool. If you are wishing to focus on them to see as much as possible, you will want to go out to either the boardwalk(Epcot) or the walkway near the pool(HS).
Just got back home last night . We ended up walking down the pathway to HS (not a bad walk at all) and had a great view and could hear the music on the pathway not too far from the entrance. We just sat on the grass on the pathway. I'd probably want to bring something to sit on as the FL grass is very different than back in MA