When we did this last year we were told to get there around 30 minutes early. If you get there too early they won't let you onto the balcony but you can look around inside the gallery. I am assuming the first Fantasmic is around 9:00 so if you get to the Disney Gallery at 10:00 for the 10:30 show you should be just right. You are going to love doing this, we have actually done it twice and will do it again the first chance we get!