I live in an area where two different languages are spoken.

I would say the ratio is about 40/60 (Swedish/Finnish) in the languages, and the 60% is the language that i dont speak, and it is almost impossible to know what language they speak unless you try to sneak closer to hear what they speak.

So my question is, how to proceed if you go talk to the girl and it turns out she speaks a language you dont speak. Should you just "well thank you" and move on? Or is it a viable option to change to English if she speaks it?