I know two kinds of expats here: those who make no effort to learn the language and those to whom not learning it would never cross their minds. Most seem to be in the first group though I know one man who abruptly decided to take the plunge and is now actively studying.
I started before moving here, continued here, then got discouraged and dropped out for about a year. Now I'm back into it. On the one hand I forgot a lot of words, on the other hand my comprehension is picking up fast and I can read anything but a newspaper, and when talking with someone I know it no longer sounds like gibberish, though there are still a lot of words go by too fast.
You really need to practice. Weekly lessons aren't enough. Making lists of translations isn't enough.
Problem in Cần Thơ is that people come from everywhere and sound so different from each other. With my neighbor I can talk about abstractions; with the guy who does our house repairs, I can barely tell he's speaking Vietnamese.
Friends and I meet a few nights a week at Trung Nguyên at Big C, anyone interested in forming a group? Both Vietnamese and westerners.