I would say a minimum of an hour before the fireworks and possibly longer since you may have to wait for a table to open up. You can see them from 'Ohana or from California Grill.
On our last trip we ate at Ohana's and then went out to the beach area while the fireworks went off. We laid in the hammocks and watched the show while the kids played in the sand. It was so relaxing, laying in those hammocks after walking the ten miles around the parks!
I would say a minimum of an hour before the fireworks and possibly longer since you may have to wait for a table to open up. You can see them from 'Ohana or from California Grill.
Make sure to request a window table. Tell them you will wait if you must. How many is in your party? Its a great place to see them. They lower the lights and pipe in the music.