Yes, there is indeed a town called Rumia in Poland, and I find this coincidence quite interesting.
Also, I think it might be a good idea to add the poland tag.

Welcome to Rumia.
Population: edible

There's also the Rumija mountain in Montenegro, if anything.

Ah yes, Yukari sent Rumia back to her homeland for a nice little homesick visit.

(My headcanon is that Rumia is Polish because of... you know, this fact right here, namesake pun.)

Also there's more images about this fact,
2 of them are Rumia dressing in traditional Polish women's clothing.
this and this