Also, I suggest that you ask staff at your hotel for a hair salon that gives head massages. It's a real treat for me when I go to Vietnam. They are not positioned for tourists, so likely no one will speak English. No worries, it's pretty simple to work out what you want. Get staff to call ahead so they are expecting you and get them to write out the name and address on a card for the taxi driver. It's typically one hour for shampoo, massage, and dry.