There is an open issue where updating location doesn't seem to be working for some people. I'll look into it, if you have any usability suggestion please get in touch: https://github.com/brutasse/djangopeople/issues — thanks!
The old Djangopeople hosted avatars but I've switched to gravatar. So just updating the gravatar associated to your account's email address should do it. I'll make that clearer on the site.
I don't see anything 500'ing on our side. If you could fire up a debugger and see what's being sent to the server and the response you get back, that'd be great.
The homepage actually only show the most recent signups. Since we announced the site at Djangocon Europe we got lots of signups from there. The homepage will need some improvement, I'll look at changing that to some sort of density map.