Depends on the genre for me.
If I pick up a science fiction romance, and it's obvious from the book blurb there are going to be two characters falling in love, then I know what I'm getting myself into, and it's fine. Everything is set up for the story to go there, if ya know what I mean.
If I'm picking up a science fiction adventure and I'm caught off guard because the author didn't set up a romance, or it's a very minor part of the plot, then I'm probably going to be annoyed the story went into graphic details.
Also, the more familiar I am with the characters (i.e. if it's a series and I've known them a while), the less I want to read about their bedroom relations.