My family is pretty much the only group of people I wouldn't talk about sex with; it's just...awkward. xD
Other than that, I don't typically bring it up, but if someone else brings it up, depending on the topic itself, I am perfectly fine talking about it. Like, talking about sex life Since i have none I am fine with, but like, fetishes and whatnot (which I have been asked about. xD) I am more leery of discussing with just anyone.