/ Which is the BEST, EASIEST to learn & most helpful"POLISH FOR FOREIGNERS"course?
The best text books are the Hurra Po Polsku series... recently published, colour, CD's, Exercise book etc, but they are in Polish and so you need to work through them with a teacher or in a class. And yes, you can learn from books written in a language you don't know, if you have a dictionary and patience... but it's not ideal and you should have so many questions about the grammar, the endings etc. that you need to ask them somewhere.
Teach yourself Polish was no good for me as it comes in at far too high a level, which disheartened me. And now I am at a higher level, I have no desire to return to it.
I would not recommend Polish in 4 weeks because there are some words in there that should carry an "UWAGA" notice. For example, in the first chapter (maybe second) you learn how to ask for a cloakroom ticket and it doesn't say this is also the same word as for a quickie.
BYKI is good for pronunciation and vocabulary, but at some point, you need to speak to someone else who either speaks the language or is learning it.
And there are somethings in Polish with Polish subtitles, but not so many... personally I liked the soap opera "The Londoners" which you can get on DVD. You can watch it with English subtitles or Polish and the dialogue is simple and the story entertaining in a far-fetched way.