I too have the cruise bug. I am serious about finding my first cruise and was primarily interested in the Mex. Riviera 7-day cruise. I like the May timeframe.
I too found the Singles Cruise Michelle talked about 'Western Caribbean' out of Tampa. That actually sounds like the best option. It spans the Memorial Day weekend. I talked to the SingleCruise.com company that is selling that trip and as of today there were 30-singles that have purchased (with an even 50% split: men/women).
I am nervous about a roommate idea as 'you never know'. I am a non-smoker and a social drinker. If you would like to chat more about this I would oblige.