I have posted on this topic a few times before. I used to travel to PNG for work years ago and things have only gotten worse since then. The multinational company I used to work for had a policy for not sending ANY females to PNG due to the high risk of rape and assault.
Simply put, if you have ANY choice, turn down the offer and move on.  It is not worth it. It could be safe if you completely restrict your movement as most expat nurses do by staying inside their accommodation or going on supervised trips for shopping etc. But that is no way to live.