It's not very common but it does happen.
I think it's more common for PL girls to date non-polish guys than for PL guys to date non-polish girls.
And if you're an Ashkenazic Jew from Poland, chalilah o b'tzlacha
-- it doesn't happen or you're out of luck! My Lipsk nad Biebrzą-born Anusi
great-granddad learned the hard way when his Bose-born ima Anusi'ah,
Aleksjondria Alicja Andrulewicza Chernetska, almost sent my American, Slovakian-Polish-American-born great-grandma to the mental institution. Long story short, he got Mary M. Trudniak of Ashley, PA pregnant and chalilah
that he would marry that Kacwiner's daughter (Her dad was born in Kacwin as, as far as we know, a goy m'Slavavakh