The direct translation of Не все ли равно? is something like "Isn’t everything equals?" or "Aren’t all things equals?"
But as usual the proper translation of "who cares" depends on the context. Не все ли равно sounds more or less neutral to me as well as Меня это не интересует or Мне все равно, while all the others seem to be стилистически окрашенными (I don’t know how to say that in English – stylistically coloured?). Мне плевать and Мне пофиг sound impolite whatever but we can hear them on every street corner here.