Use English in Poland, Czech Rep. and Slovakia and Russian or English in Russia. You can also learn some basic words of Czech, Polish, and Slovak many of them are quite similar, some of them have completely different meanings despite of the fact that they sound the same, what is a reason of some funny language misunderstandings. For example Polish word for "to look for" means completely other activity in Czech. I would advise you against to use Russian in Poland, Czech Rep. and Slovakia. If you were Russian tourist it would be no problem, but you are not Russian and everybody will realize very fast that it is not your native language. Than some people (of course not everybody) could ignore you or be passive to such kind of tourist because many people in these countries don't like when somebody from other country (especially from the west) looks at them from Russian point of view. They just receive it as if you ignored the fact that they stopped to be the members of Soviet bloc many years ago or as if you didn’t notice the difference between “all of these Eastern Europeans” what is just offensive for them. I think it would be even better to use German than Russian .