I've only been to such a place once, it was by invitation, though I will admit that it was....hmmm... eye opening.

The only consensus on dress that I noticed was as follows.


.... I have never seen so many "little black dresses" on the women, and on some people who were not women but appeared to be, in one place in my entire life.

Personally I showed up in running shoes, blue jeans, a dark green chamois long-sleeved shirt and a bomber jacket. I stood out like a sore thumb but that didn't bother me much.