People in the tourist industry in Barcelona speak English, usually. Remember that English is spoken, to a greater or lesser extent, by people from all of the world, especially the travelling population of the world. So the person on the hotel reception desk in Barcelona or the bartender in Warsaw will not only be speaking to you in English, but also to visitors from Hungary, Japan, Sweden, Russia, Turkey, etc, etc...

But do try to say at least "hello"and "thank you" in the local language.