This past weekend (May 17-19), the hacker group in my local area HackMiami had their first conference, HackMiami 2013 and I attended. While not a member of the group, I have heard of them, and we've had them help out with some of our South Florida ISSA events. This is not an underground group. Most of the members actually work with/for many local IT security companies.
This was a hacker conference, which is a little different from a traditional IT Security conference. Some of the stuff done is a bit out there, there is expectation that the audience is more technical, and some sessions were more hands on then in most Security conferences.