Yes you can see some, we saw them as we were leaving the park and heading toward the trams, and could still see them from the Mickey & Friends parking structure. You can even see the high ones from the Los Sanchez restaurant all the way on Garden Grove Blvd. which is a good 10-12 minutes away.
If you want to see fireworks then yes you will see some from Downtown Disney, but if you want to see the greatest fireworks show on Earth then this can only be seen from inside the park and with a "front of the castle" view due to the music sync and other castle effects.
When you are away from all that and especially the music the fireworks sound extremely loud, like you're in the middle of a battlefield.