Bigos
Yes, yes and yes! Love me some Bigos!
Żywiec
If you are in a place selling good traditional Polish food and the only beer they have is Zywiec, walk away. It's the Polish equivalent of Carling or Tennants. You should be able to find a lot of places that serve much better beer.
Cutlet
Kotlet Schabowy may not be the national dish of Poland, but it's something so many Polish people that live outside of Poland miss. It's simple, delicious and pleases everyone.
Can I also suggest polish pancakes (naleśniki) with savoury fillings, really really tasty! Also if you are lucky enough to have a market in the square when you are there. Grab some grilled meatstuffs!
Oh and Golonka...I could go on!