Like has been said, the Czechs will have had to learn Russian. In a large number of European countries (in ones where English isn't the main language), English is the first "other" language taken at school these days, then normally German/French/Spanish, and generally the standard is very high.
Most of the Czechs I've met have German as a second language these days and many are fairly fluent, and English after that. A lot of them (not sure if this is representative of the country as a whole though), can also speak Slovak and other Slavic languages.
To be fair to Jagr though, his English is pretty damn good, it's just that he has a thick accent. He can speak it fluently enough to talk to the press, and to teammates and coaches, and that's all he needs. Sure, Lundqvist sounds more fluent (listen to Daniel Alfredsson too, he sounds Canadian...), but he's been learning it since he was a kid. Jagr hasn't, and it's often difficult to learn a language when it's forced, rather than taught. He moved to the US and had to speak English, and it was his first year or two of learning it.