I think the assumption generally is that some women will feel uncomfortable with a sex jokes in an audience where they tend to be a small minority. My experience as a man is that women in groups are at least as prone to telling dirty jokes as men, but I can understand that if you're one of a handful of women in a room full of men it might feel quite different.
As the IT guy in a variety of medical offices who's known for being pretty laid back, some of the discussions that have happened when I was in the room are filthy. Also, sometimes folks forget I'm in the room.
The most memorable and amusing was the discussion by several women (some busty) of "[flopping them on the counter]", but there have also been discussions of men or parts thereof.
