My hubby and I will also be there 10/28 - 11/4. From what I understand, Playa is hot and sunny in October just like any other time, just gets a little cooler at night. There will probably be daily rain showers that last a couple minutes, but that happens anyway.
I wouldn't worry about not being able to sail or snorkle - unless there's a huge storm or something unforseen - you should be fine.
There's tons of good info about the weather and what to expect in October/November on this board, just do a search and I'm sure you'll find answers to any questions you have about Playa. The people here are really great.