I’ve done a fair amount of flying in Poland, but always in my own aircraft. If your licence is a JAR PPL (or better), it is acceptable at face value for flight in Polish aircraft within Poland.

Most of the smaller fields have schools available, and prices are reasonable, but rising all the time.

VFR flying in Poland is fairly straightforward with the only barrier being a language one. Smaller fields often provide limited FIS in Polish, or occasionally fractured English.