Two months would certainly allow you the opportunity to travel outside of ther capital - that obviously depends on your time commitments,etc.
I am also going to Krakow and and Upper Silesia too (I am obsessed about the 1919-1921 uprisings there), but I don't know if the museums have bilingual signs, as do some in Warsaw and Wroclaw. I am taking some Polish classes now, but I don't have a solid grasp of the innumerable cases.