Vincent is great, he was $20US/person last Feb at least. He has equipment but we always make room in our luggage for our own masks and snorkels (I also bring my fins...) - I don't like sharing this stuff and really like to know that our gear will fit (not leak) and perform perfectly. Its good to have your own equipment as you may also want to swim around off of your resort - not much close by for most of the beach, but you can see some cool stuff (or just float endlessly and become one with the sea) off of most cliff resorts.

Dive shops have the best gear but even the stuff at Costco or Walmart-type stores are way better than the equipment in Negril.