Poles have some pretty delicious meals outside of pierogis. There's barscht (cabbage soup), zurek (a kind of sourdough soup), golabki (meat-stuffed cabbage leaves). Great pretzels too.
My tips are: barszcz czerwony z pierogi (both red made from beetroot with a good pierogi), barszcz biały (white borsht - basically like żurek, but made with wheat and served with with meat and egg), żurek (a fermented rye soup), bigos (a stew made with cabbage, sour cabbage, lots of meat and sausage and other ingredients), gołąbki (as you said - cabbage leaf wrapping meat and rice filling, served with a tomato sauce), kopytka (a little like gnocchi), łazanki (like a polish lasagne, but with sour cabbage), or just something simple like kiełbasa z cebulą (sausage with onion fried.)
So much great food. This is only scratching the surface.
Cabbage soup is called kapuśniak (from "kapusta" which is cabbage). Żurek is a fermented rye soup often called "white borscht" on North American restaurant menus. Another Polish soup worth trying if you find it on the menu and like sour flavors is zupa ogórkowa, which is a dill pickle soup.