We just got off the May 25th sailing of the Fantasy. It was a full cruise, and the pool deck was super crowded during the pirate party and fireworks.
That being said, I watched them standing on the port side of the pool deck, next to the towel bins by the drink fountain. My family (who I could not find) was on deck 12 starboard, next to the stairs by the forward funnel. We all had great views, since they are shot from the back of the ship, towards the front on the starboard side.
Basically, anything should work on deck 12 or 13 starboard, or deck 11 as long as you aren't underneath deck 12's overhang.