The expression isn't really so idiomatic. It literally translates to: one will see you (around). I think the implied idea would be that we're not going anyway (far away) and will bump into each other in the near future. I live in NRW, you can use this phrase in casual conversation. Although ciao, or tschüss are more common.
@Raisinnoir Your argument is really foolproof! If they said 'Tschüss' (which is written with umlaut) or 'bis später'(which is also written with an umlaut) then there CAN'T POSSIBLY exist any other way of saying it. Just like in English. You only say 'see ya'. There CAN'T possibly be any other way of saying goodbye... That's how it is... This is the third time I've read this type of fallacious silly argument in this discussion. Not very smart, really.
"Nordrhein-Westfalen" in English "North Rhine-Westphalia". The most populous state of Germany, home to the Ruhr region the largest urban agglomeration in Germany and third-largest in the European Union (copied from Wikipedia).
Another abbreviation for a German state is "MV" for "Mecklenburg-Vorpommern" (Mecklenburg-West Pomerania), other states are normally not abbreviated in speech. "MV" and "NRW" are the exceptions there. They are like DC in this respect.