drasc We call ourselves "Slezsko" and we speak Czech!
Silesian language sadly died out in Czech, so I don't speak it aside from a couple of phrases. I know that Polish people call that part "Śląsk" and Polish people in that area can speak Silesian (some of them) but it is not considered an official language and you still have to speak Polish at places like schools and townhalls, etc. BUT, they do have dual-language warning signs and similar! The Silesian part of Poland is fighting for the Silesian language to become the region's officially recognized language, so hopefully one day!
Apparently, there's also a big German population in Poland (we used to have it in Czech too, part of my family is German) but after WWII they were forced to leave. This German population calls the Silesian area "Schlesien".
I can only speak on behalf of the Czech part of Silesia though!