Saigon (sorry, I like that name better), is chock-full of massage places. There are lots of choices to be had. Cabs are cheap, they speak english and will get you to the action in a hurry.
But try to get out of the city and into the countryside. Vietnam is a charming destination, and the women there are nubile, spinner-types, shy and demure. They crack smiles easily with Westerners, and you can easily start up conversations leading to ???
Other recommended locales: Dalat, Danang, the Imperial city of Hue and the mountainous regions in the west. Hanoi is not worth the trouble. Being the administrative core, it is more rigid and traditional, and you are unlikely to find the entertainment you are seeking there.
Have a nice visit!