General cost of living in south Viet Nam? Any additional advice?

If all goes according to plan, I'll be coming to VN for about six months in January. I was there 2.5 years ago (for only three months) and worked in Nha Trang, and this time I want to stay longer.

I'm going to probably work for my friend's school, and he'll probably scope out a couple of places for me before I get there. I was renting a top-level hotel room for a reasonable $250/month, but this time I'll be renting a house or apartment with another person. My friend said I can easily find a place under $400 in the main drag where all the tourists are, but I don't know how much I ought to expect for utils and stuff. Since rent will be split at least two ways, I'm willing to fork out a little extra for A/C, good view, and all that jazz. I peeked at Nha-Huoung, which had some excellent deals, but it doesn't mean what I want will be available months from now.

When I was there last, the dong wasn't as weak as it is now, so I'm hoping I'll be able to spend a little more to have more fun. I vaguely remember spending around $30 for the cheapest Nokia phone and a minutes charge-up. I'll also be renting or buying a motorbike, and friend was saying how gas is about a dollar a liter. What ought I be expecting for other things, like electric, net, water, all that good stuff? I'm trying to make a budget for myself to live by for the next few months until I get there, so I can save money to do some traveling while I'm there while still maintaining a decent lifestyle.

Also, any other input on what's important to know? Facebook was blocked when I was there, so I was using Tor to get around a lot of sites on the horrifically slow internet, but my friend said FB isn't banned anymore. Some other things I have to remember to bring (like tampons, holy cow are they expensive there), but I can't think of all what I might want to bring that I can't get there/can't get for cheap. From what I was told, NT has changed quite a bit in the past few years in terms of construction and tourist flow, but I'm also wondering about the net, and what's good/what's bad/what I should have pre-loaded on my laptop before I get there.