Hoping no-one will mind, I have taken the liberty of copying the discussion below from the MTOA List-Serve.

We have a time constraint (I know, trawler people shouldn't have a fix timetable, but still) and to make Bahamas, we would have to be there mid/end January to mid March. Experienced Bahamas travelers say we will be cold — no swimming. Did, in anybody's opinion, the global warming change that, or should we wait until we can make April/May, or the global warming kicks in?
Raoul, ADRIA

Raoul,
We spent time in the Abacos at the end of April the first of May and it wasperfect! The charter company told us we were lucky because it was the best weather they had experienced all year.
Happy New Year,
Susan Wigginton

I can tell you that those of us who live in Florida seldom go to the Bahamas in the winter since the same fronts that pass through here also go there.
That being said, there is also quite a difference between the northern islands (Abacos) and further south. I am sure many people from northern climes think Georgetown in the Exumas is pretty tropical even in the winter.
Bottom line, it is up to you, but if you want beautiful clear blue waters the Bahamas are pretty tough to beat.
wayne

Raol,
We have been in the Bahamas in that time period many times, We swam, snorkeled, fished and played volleyball on the beach every day. It was sunny warm and fantastic. We would be there now if
circumstances were different but will make it next year. Even the Abacos are warm but the fronts do make it through there more frequently. Head for the Exumas and have a ball.
Chuck

We spent the winder in Marsh Harbour 2 yrs. ago. Although windy most of the time that year, it was very comfortable for swimming & snorkeling.
George 

April is the best month for weather in the Bahamas pr the Florida Keys The winter winds are down(making the stream passable)to the Bahamas, and the Keys water temp is warming up as well. The days are much longer, and the snow birds are heading north making the harbors less congested.
Al Hackett
Pale Moon

To avoid the winter wind cycles, it's best to wait until April. We've done it the last three years from April through July and have had great weather.
Bob & Susan