Good day, fellow forumites!
I'm a guitar teacher who's fluent in Spanish, German and English. As of late I've been learning a lot of Polish on my own, since I've been planning to try my luck in Poland in the near future. Can anyone tell me about opportunities for music teachers?
Next to non-existent. Professional teachers will have a lot of qualifications in music, often university level - you won't find much demand for a foreigner that doesn't have such qualifications.
If you're qualified to teach music to school children, then there might be possibilities there.