Here's ~5 years tango dancer @ HN :) From where I am now tango actually seems an unnatural choice for nerds. Of all the social dances tango is one of the most intimate in terms of personal space, which makes any nerd nervous and clumsy. On the other hand, it seems like one of the least physically demanding - check out Buenos-Aires 70+ grandpas on YouTube. I think it is a combination of two: crave for intimacy plus actual ability to imagine oneself as a hero of those videoclips, as opposed to fit and dexterous lads from swing and boogie-woogie, or half-naked machos from salsa, kizomba and bachata :)

There is also a point of general availability. When you check out your typical dance studio around the corner, there are salsa, hustle, swing and tango. Of those aforementioned tango seems most promising from romantic point of view.