Here's my guide to what I consider the best places to snorkel. Plenty of other popular spots, like Eden Rock, Cemetery Beach, Governor's Beach, etc...can be found on the tourist guide sites.
http://snorkelblog.tumblr.com/

January may be windy on the North Side and East End, but the Seven Mile Beach side is the leeward side and usually only gets up to breezey.

Some favorite upscale restaurants:
The Brasserie
Calypso Grill
Morgan's
Catch
Tukka
Kaibo Upstairs
Luca
Grand Old House (food has been waning a bit as of late, but love the setting)
Le Vele
Cocolobo at the Kimpton

Some activities:
Sting Ray City
Bioluminescent Bay Kayak or Boat trip
Crystal Caves
Pedro's Castle for a historical perspective
Sunset Sail to the Rum Point Club Restaurant for dinner

For rental cars, we use Orbitz, Expedia, etc...to find the cheapest. Some agencies have slightly newer cars or better/more efficient check out/in processes, but most are generally fine.

Snorkel air just tastes better than canned air...