In reply to Miroslav Glavić.

Good question! I only speak English (and a little bit of Spanish), but I've found that most WordCamps will at least have some sessions in English, if not an entire track. While WordPress is an international product, most of the communication around working on core and building sites/plugins/themes happens in English.

In most of Europe, as you know, most younger people speak English, as it's a common language between countries (sorry, Esperanto). This is less common in South America and East Asia (I'm told, haven't been yet). Here in India, everyone speaks English, and many of them speak it better than I do :)

I've never had a problem traveling places where English isn't the primary language-- a smile and some body language can go a long way to bridging the language gap.