I'll move to Saigon in April and found a house to stay, but there's no wifi. I really need to work on my jobs based in Hong Kong, and I work at random hours, so places like Starbucks are not suitable. It should be a wireless that is reliable and fast as I sometimes need to upload huge graphic or video files. I'm thinking of using these 3G usb keys, have you tried them in Saigon? Taking a subscription can be possible, depending on the minimum period. Not sure how long I will/can stay in Vietnam, but at least 3 months.
Another possibility is that I share an office space, if it is accessible 24/7. I'm a freelance designer for events, so the working hours vary.