Hey Gus,
Mike has it right - Rangiroa is a must dive location. I also talked to alot of divers and wished that we would have done fakareva instead of Bora Bora. FYI it is only a 10 minute jump flight from Rangiroa. Both of these locations are huge atolls with massive reefs. Finally, I would suggest stopping off in Moorea. It is absolutely incredible physical beauty, with lots to do, especially if you like hiking in rainforests. It is also one of the most affordable places in FP. Speaking of cost, we did not find FP to be much more costly that other places we have vacationed i.e. nice dinner was $25-35 per person, decent bottle of wine $35-45, no different that a decent restaurant in LA. Hard alcohol drinks and beer are costly at the hotels. If you are on a budget, go to the local markets, and you can buy juice, food and beer very inexpensively compared to the hotels.
My dive operator was Top Dive and I would highly recommend them. The DM's in Rangiroa where some of the best (unobtrusive) I have experienced.