There are cruises from New York that go to Bermuda. Although that might not get you any younger of a crowd than the Canada cruise will. I think RCCL does one from New York then gets to St Thomas but that may be a much longer cruise than you can manage.
You never know for sure what the age mix of your cruise will be until you are on it. Especially with the economy the way it is you may find many more people doing the same thing you are planning to save money! Go for it. Even if you don't find a bunch of singles, there is so much to do on a cruise, you will still have fun.
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise
NCL Dream October 2006, RCCL Mariner OTS June 2007