Which deck would depend on how much exposure you want on your balcony. We like the mini-suites on Dolphin deck; but they are completely open and some people don't like that. Our privacy has never been an issue and the cabins are nice and light and airy. There are some mini-suites aft on Emerald deck that are covered.
Many like Caribe deck because the balconies are larger than the standard balcony cabins and are partially covered; you have some privacy, or you can be in the open.
The balconies on Baja, Aloha, Riviera and Lido deck are covered (by the deck above) and more private, but smaller and not as light. The cabins on Lido deck give you easy access to the pool areas and Spa.
There are some really nice aft-facing cabins nestled in between the suites on Emerald, Dolphin, Caribe and Baja decks. They have very deep balconies and great views. Personally, I think that makes the cabins a little too dark.
As for location, I would suggest anywhere between midship and aft simply because that is where most of the venues are. The farther forward you are the less foot traffic you will have past your cabin and the quieter it will be--but you will also have to walk farther to everything except the Princess Theater, casino, Atrium and Spa. I like a cabin near the aft elevators and stairs because my favorite spot on the ship is the Terrace Pool, with its proximity to the Horizon Court buffet and Outrigger Bar.
I've heard very few noise complaints about any location on the ship.
I think other than a suite or mini-suite, my suggestion would be a balcony cabin on Caribe deck between midship and aft and your best value would be from C701 to about C723; that puts you in catagory BB instead of BA. You will save some money and still be near the elevators and stairs.
Sorry, didn't mean to write a novel; it's just that I get excited about planning a cruise--even helping with someone else's.