Polish is generally a quite homogenous language, there isn't much difference between what is spoken in most parts of the country.
But apart from Polish, you have also Silesian and Kashubian, and in the south all kinds of subdialects that are called (an umbrella term) "gwara góralska" (highlanders subdialect?) That of course includes 'accent', but there are a lot more differences, mostly in vocabulary. I don't really have much knowledge about it.
I believe that most of people speaking such dialects* should be able to switch to more or less standard Polish, though.
*Well, Kashubian is considered a language, but there's no agreement about Silesian among the linguists.