DON'T buy it before you go. There are exchange places everywhere, everywhere accepts credit cards and there is no problem whatsoever.
I have spent most of the past 20 years in Poland and therefore feel rather qualified to answer.
Do you know if it's a problem getting ZLOTY in Poland or should we get some before we get there ????---We should be there in July on our way back from Finland===do you know when you will be there ??===Thanks
All the best
Nigel & Pamala