Budget stay in Vietnam

Hi,

We are a group of backpackers touching down on Vietnam after Thailand and Cambodia. We will be travelling upward from HCMC to Hanoi for 12 days on early April. We are facing some problems in locating trustable, and budget stay for 1 or 2 days around HCMC, Nha Trang, Danang, Hanoi. Hope that advises from the fellow Vters would allow us to resolve the problems. We are planning to travel to Halong Bay in our last few days of stay in Vietnam to sum up the entire trip. I've visited a few websites on travelling agency that organises the Halong Bay 2D 1N stay. I'm pretty interested in the trip, but the prices are too high for us students to afford. If there are any recommendation on budget Halong Bay trip, I would not hesitate to take up the trip to enjoy on the beautiful scenery not to be missed. Hear from you guys soon!