Hi Caroline
I am not going to Vietnam on the date you are but have been twice, and would like to say I really enjoyed myself. I have visited all the places on the tour including Dalat, which is in the highlands.When I went I found the people to be very friendly, and often stop you to ask questions, some of them personal (do not be offended by this it is only because they are interested and want to improve thier English).
I hope you have a really enjoyable holday
Lesley