Last summer, we did the early Fantasmic and they had us exit on the behind the scenes route that dumps you out right inside the front entrance. It was about 10 minutes before the fireworks were starting. We weren't interested in staying for the fireworks so we headed to our car. By the time we walked there, they started and we sat and watched a bit from there and then drove off as soon as it was done. So timing wise, you can do it, but if you were trying to get a prime spot to view them in the park, you'd have a hard time because it was packed when we were leaving.