I agree with DLR29. The RDCT show is much more than a fireworks show. If you watch them from outside the park you will miss 90% of the show. If that is the only option then go for it, but do not mistake that for actually seeing the show because you will only be seeing 10% of it.However, I don't recommend seeing the fireworks from outside the park. It really is very different (and better) with all of the special effects from in the park.
I am not 100% sure on this but I think that there are some rooms at the Carousel Inn and Camelot Inn and Suites where you can see the fireworks.
The Howard Johnson has Disney View rooms available.
We watched the fireworks from the balcony of the Camelot, we could also hear the music. Even that far away the booms were too loud for DS.
Looking for a DLR hotel close to entrance and can see fireworks