Like everywhere, PNG has law issues. Maybe not tackled effectively like developed countries.
My advise is to make friends with locals. I know alot of °µÍø½ûÇøs who now calls PNG home. I have come to know and made friends with °µÍø½ûÇøs who can go shopping on their own.
Yes, follow the "unwritten rules" of the society. We still value our culture.
I guess safety is an issue everywhere.
Generally, PNG people are very friendly and caring, especially if you are from another country