It is much better to say بخير then to say تمام. Teaching people a mess of dialectics and modern standard arabic is not going to help them. Either you learn a dialect Arabic from Morocco, Syria or Egypt, or you'll be studying MSA, because intertwingling the two only causes people to not understand you, (which is the problem of the dialects).
Personally, I think that learning dialects along with MSA is the best choice because, unless they don't intend to communicate verbally and only want to read newspapers, that is what most people are going to need. I know that from personal experience.