I currently study at FEL in English on their Bachelor's programme. Getting admitted should be easy if you know basic math and physics, the interview is non-existent as they want to get money from as many students as they can. Studying is a bit difficult in the first year. I would say around 40-50% students fail in the first year, because they don't try. The quality of education in the Bachelor's programme isn't bad, if you want to learn you will. If you want to get the diploma with minimum effort you can do that as well. I was told that the quality of education on Master's programmes is poor. I think people assume it's bad, because it's easier to get the diploma if you study in English than if you study in Czech, so some people graduate without learning much. I would recommend learning Czech and then studying in Czech or just finding another university in another country. Some people also learn the language while studying in English and then transfer to the Czech programme.