I have not done one of Windjammers singles cruises (becaiuse I am not single...VBG) However, I have done the Legacy to the BVI and had a great time. Like MsSocial said, it draws an exlectic group of cruisers that I am sure you would enjoy.
I did talk with some of the folks on the Legacy and got the impression that the singles cruises do tend to "pair up" as the cruise wears on, but I doubt that it is expected in any way.
Let us know how it goes. What ship are you looking at?