Being native Russian speaker, I should say that for me the issue is far less stressful than for my pals. Firstly, the language group is the same – Slavik, so I can naturally catch some general sense out of the speech. Furthermore, there is this group of people (especially of older generation), who speak Russian. Once I even managed to get an unexpected discount at the flea market because of it. Generally speaking, some basic Czech words are required to fit in the community better, because even though the majority of people do speak basic English, it is sometimes easier to reply or ask for a price or navigation in Czech. At the hospitals, for example, the situation ranges a lot: in big municipal hospitals there are special foreign departments, but it is always better to ask for help from locals in advance.