Visiting Vietnam (Ho Chi Minh City)

Hello
I am an English guy living in Oslo, Norway. I'll be in Vietnam on holiday (HCMC, Phan Thiet and Nha Trang) from the end of next week. I don't see many activities planned, so I wondered if anyone would like to meet up for a drink, have something to eat or, if not, suggest where to go, what to see, what's a must, where to eat, what to do, (what NOT to do), or any other pertinent advice.
It's your big chance to make someone happy!
My fingers are crossed!!
Kind regards
Neil