Don't stress about which university you attend, but rather focus on making as many contacts as you can here. There are opportunities for foreign actors in Poland, you just need to be very, very good at networking. PWST is a good choice, as Kraków has a huge artistic scene and there are plenty of opportunities there. It's also a well known, well established centre for the dramatic arts.
Nana be realistic. You want to study drama of all things in English in a country where English is not the native language and where English is not widely spoken. Obviously most drama degrees will be in Polish. As for rankings, it might get you through the door of an agent, but at an audition the casting director will not care where you studied, he'll care about how you read the lines and whether you're right for the part. If you're talented, hard working and determined you will have as much chance of success as anybody else regardless of where you study.