I didn't much like the SD trip I was on, and I worked as an instructor on the trip, so I had an "insider's" perspective. Plus I'm a dive travel professional, so I do know how things are supposed to work. Therefore, I would recommend caution if you consider traveling with this organization. When volunteers run the show, there are inevitably lots of problems, organizational mistakes, etc. SD is a business--when I deal with a business, I expect professional-quality organization, not the amateurish result I had with SD. But for some people the social aspects of the SD trips outweigh the glitches, and as long as the diver has the correct expectations, it can work out fine.
Rather than going the SD route along with their frequent problems, you can participate in SB's own BuddyFinder option.
Or just book a liveaboard as a solo traveler.