My friend and I are visiting Krakow and Prague and we're really into folk dancing?

There is a very little chance you will see folk dancing in these cities. You will need to head out to countryside, especially into Moravian countryside. Folk dancing and various folk related events are common in southern Moravia or Vallachian region of Beskid mountains. These places will have some events during the spring till fall months related to harvests or village life. In Poland you will see these events in mountain ranges close to Slovak borders. Slovakia has also decent folk art and events. Outside countryside, there is unlikely you will ever see any folk dance, and majority of Czechs are not even aware any of these events.

South Slavic folk dances:

https://www.youtube.com/watch?v=UiPcuMUrJKY

https://www.youtube.com/watch?v=SnFbVrThutU