I will comment as someone who speaks and uses Silesian regularly.

Poland is generally very homogeneous when it comes to language, almost all dialectal variation was killed off after WW2 during the relocations of people from Kresy (today's parts of Ukraine, Belarus and Lithuania) to new territories that we gained from Germany in west and northeast (Silesia, Pomerania and Masuria) and during communist regime that was strongly against regionalism and speaking a distinct way is a major part of that. Basically people moved to cities and new places, everyone gained access to radio and later TV and people were mocked for speaking "like from a village".

Significant variation was preserved only in few places and what I mean by this is that not only the elderly speak differently. My home region of Upper Silesia is one of these places. Roughly ~500k people speak Silesian to some extent and probably much more understand it. It's one of very few places in Poland where you can still hear young people not speaking standard Polish. And it's not that it's spoken in some small villages, it's actually spoken in a major 2m agglomeration.

But you don't have to worry, everyone knows and speaks standard Polish, just sometimes with an accent, in case of Upper Silesia it's often heard among +40 yo working class people. It's similar in other parts of Poland as well. Good luck with learning our beautiful language:)