My last trip was mid-late October (we left literally right before Day of the Dead unfortunately) and the weather was great - we had a couple storms (including a gorgeous thunderstorm one night), the water was warm and the diving was fabulous. The currents were unusually strong at a few sites but it all worked out - the only real drawbacks were jellyfish (lots of them, but not dangerous ones) and some of the resorts had limited menus for the low season - not really a huge deal thanks to the plethora of amazing places to eat, but if you have a love of some specific resort's dinner menu, you may want to take that into consideration.
The previous trip was in March or April (I don't remember exactly which) over spring break, which definitely brought a fun, party atmosphere out and the island was much busier.
The previous trip was in March or April (I don't remember exactly which) over spring break, which definitely brought a fun, party atmosphere out and the island was much busier.