Hi athst,
Thanks for your comment and questions. We went with "sportspeople" because our research showed it was regarded as meaning "people who do sport" in the most places - in the UK, for instance, "athletes" is often (but not always) interpreted as referring specifically to people who do track-and-field athletics.
You're quite right, we're not aiming to be a sports fan site - we're very much focused on the sportsperson/athlete. We're not really a Meetup-for-sports, though (although obviously it's great if our members find new sporting partners on the site, and many have already). In fact a huge amount of interaction is between people who are never likely to meet; a Scot who cycles 100 miles before breakfast encouraging a mother-of-two who's working towards their her 5k, for example. It's been great to see how our users will give motivation freely, no matter what someone's level.
On the question of locale-specific Tribes, we certainly have a few of these, and users are welcome to create whatever Tribes they would find useful. We also have event-specific challenges for specific marathons, which are naturally localised. What we've found, though, is that our users seem to respond best to Tribes and Challenges that are globally relevant; things like the get fit without joining a gym Tribe (http://tribesports.com/tribes/get-fit-without-joining-a-gym), or the 5 minute plank Challenge (http://tribesports.com/challenges/hold-the-plank-pose-for-5-...).
You're absolutely right, though, more location-specific resources for users will be a key feature in future, and it's certainly something we'd like to develop further.