You might also give your order of preference of what you want in your view. Otherwise, if Sierra high floor DTD side is not available (after all, it is most in demand and is partially reserved for conceirge I think), you might get Sierra Tower on the pool side (no fireworks) or a lower floor. You can actually get a fireworks view from parts of any of the towers. If fireworks view is your primary concern, I would suggest you request "a fireworks view, preferably in the Sierra/Dreams tower". I just think its a good idea not to sound to specific or demanding in your request and to convey that you understand that your request can't be guaranteed.
I also agree that calling in your request around 3 days ahead of time is a good idea. It's worked for me.
And hey, maybe I'll get your room after you check-out. I'm planning on calling in a request for Sierra/Dreams, preferably with a DTD view. (My TA already put Sierra preferred when he made the reservation).
