Let´s do it the other way, if a learner of Portuguese, from an English-speaking country listen to Portuguese.
Firstly, would be advisable that he would learn from an educated people, I mean, the one that knows the minutes of Portuguese, regardless of wich state he was.
Then would be prefferable that he listened the Portuguese of the southeast region, why? because is the one he is going to be in touch, watching and listening the mainstream media, nothing to do with prejudice here.
Now he has a working knowledge of Portuguese, then he is going to know the "niceties" of Portuguese language as a whole, for example, that some ''Paulistas" have their ''e'' with a ''ê" sound. That´s why that people in TV (game) shows are asked to pick a letter and they may say out loud ''ê", if other regions it might be ''é" sound.
Then would come the regionalisms, the garoto/moleque vs guri and so on.
Then, stop everything! chances are that he/she comes to Rio, or Sao Paulo or land in some northeastern or north state, so it would be an almost completely different can of worms then. Or maybe the speaker have a different "register", let´s also guess that he stays at friend´s in Piauí, but the family at the house if from RS, so they could talk many words that aren´t of current usage by natives/local people.
You know what? he wants to learn Portuguese, he gets in touch with Portuguese and doesn´t worry much, practice will come with time and exposure to the language. There´s a "core" of language that we really have to know, with wich he can always ask about others words and expressions that he happens to meet, so it´s a beggining, and it´s what matter much.
My thinking, tough.