I've got some friends in Krakow who don't skate but would show you around. Both dude's are rad and like to drink beer...a lot haha. Having lived in Krakow I'd be able to better advise you on it so let me know if you're heading there.
Warsaw, go to hipster platz. There are a lot of good bars, restaurants, and cafes around there. Plan B is a good one. Near to here is a street with lots of good places, a bit more posh, but head to Kraken Rum Bar to scope out that area.
Go across to Old Praha if you're into clubs or just wandering around the part of Warsaw that wasn't entirely destroyed during WWII. Karmnik is an interesting cocktail bar in the old town.
Nowy Swiat is the popular tourist street but maybe don't get stuck on it the whole time you're visiting. Karmnik is an interesting cocktail bar in the old town. Go to Pawilony for drinks around here. Cheap, hidden down an alleyway, then tons of bars on top of each other that are all rad. Pretty social area.
Piw Paw is a cool beer bar but there's some more low key ones. Lots of good beer spots in Warsaw, tons of craft breweries in Poland actually. Kufle i kapsle is another. Some of my favorite beers in the world actually come from there but you can't really find them outside of Poland. Try a Ciechan Piwo Miodowe for sure.
One of the bigger markets is here
https://www.facebook.com/pages/Gie%C5%82da-staroci-na-Warszawskim-Kole/140200286050807Lemme know if you have any specific questions or things you'd wanna see! Poland's amazing, have fun!