We've seen them twice from the bridge between BC and the BW. If you're at the BC just take the path towards BW. It's a popular spot, so it must be one of the better places to see them without entering the park.
I agree the bridge is a good spot. You can also get a little closer, the walkway to the Epcot has a few benches along it and they are all nice spots too. Either way you will only see high fireworks none of the low stuff or the globe.