I just spent the past week in Las Vegas for my 15th DEFCON, I'm male.
The conference has so many different aspects, it really is better to break it into components, talks during the day, chill-out areas, CTF room, hardware/lockpicking villages, public/private night parties, hanging out at the bars all night, etc.
Here are some of my observations (for better or worse):
* If you're a woman, expect to get hit on dozens of times to varying degrees.
* Some people are drunk during the day, most people are drunk during the night.
* DEFCON attendees tend to be the personality types that make their own rules, and aren't well integrated socially.
* There are some (very few) attendees that seem to have mental problems, don't understand boundaries, and will do very inappropriate things; at least a few are usually banned or kicked out of the hotel or conference each year.
* I chatted with a cigarette girl in the Rio at one point, and asked her if she had been harassed a lot by DEFCON attendees, and she quantified it as, "Not really that badly (in comparison to other events)".
* Small private parties at night can get wildly inappropriate (these are not official DEFCON events, they are private parties hosted by attendees), you'll find naked people in pools at least a dozen times during the con, at least 2 or 3 instances of people engaging in some form of sexual intercourse, strippers, porn playing on a display in the corner, drugs, prostitutes (seemingly not having much success), etc.
This behavior is perpetrated by both male and female attendees, and in fact the average female attendee is worse than the average male attendee in my experience; although, women being in a great minority, you're much more likely to be on the receiving end of inappropriate behavior as a woman.
I had one girl tell me she comes to DEFCON just to meet guys, and said, "I get to have sex with any guy here I want".
This year alone I had female attendees I didn't know, or just met, slap me on the ass several times, had 2 drunk girls walk up and kiss my cheek, had my nipple tweaked once, had my crotch bumped/groped/etc. 3 times, and had a random assortment of other harassing behavior directed towards me (all of this was at night during the parties).
My friend was wearing a kilt, and at one point had a girl stop him to stick her head under the kilt so her friend could take a picture, and then followed it up by grabbing at his crotch while she was down there (in this instance the girls weren't DEFCON attendees, just random drunk women in a casino).
CONCLUSION?
* If you avoid the late night (especially unofficial) parties, bars, and drunken events in general, you are going to avoid most of the inappropriate (and worst) behavior.
* Female attendees will get hit on multiple times by lonely nerdy guys, I really don't know what to say about this, but if you stick to the actual convention, you probably won't endure much worse than bad pickup lines.
* DEFCON has the weirdest, smartest, oddly intense mixture of people I've ever met that mostly come to go completely insane and push boundaries of all kinds... It does have negatives, but the experience is something I look forward to all year long.