vinaphone now has D7 plan that costs 7000 dong and gives you 1.2Gb for 24 hours of use. you don't need unlimited data when you are vacationing. i was having a hard time to finish even 150mb per day.
I use D5 plan that cost 5000 dongs with 200MB of data per day. I can't even finish 200MB every day, especially it's 3g speed. I only use it for navigation and simple surfing. Everywhere have internet, really no need to get a lot of data.