As most people now know, there are two official languages in Cataluña: Spanish (or Castilian) and Catalan. Catalan isn’t a dialect of Spanish; it is a separate language which in many respects is as close to French as it is to Spanish.

The Catalan government has spent a lot of money trying to increase the number of people who speak Catalan. Not surprisingly, some students have written to us asking whether Catalan could interfere with their Spanish studies. The answer is “no”.
At the school in Barcelona, they teach Spanish (not Catalan) to their foreign students, and their host families will also speak Spanish (not Catalan) to them.
Students may overhear some conversations in Catalan, but they are equally likely to overhear conversations in English, French or Italian – Barcelona is a very cosmopolitan city!

What’s more, everyone in Barcelona automatically uses Spanish to speak to foreign students as they don’t expect them to know any Catalan, so there is very little danger of students being asked to understand anything other than Spanish while they are in Barcelona.

Finally, it is also worth bearing in mind that all Catalans are totally bilingual and that they speak Spanish without any noticeable accent. So what Spanish students will hear in Barcelona is in fact much closer to “correct” Castilian Spanish than the Spanish they would hear in some other regions of Spain where Spanish is often spoken with a very strong regional accent.
For more information on please see learn Spanish in Barcelona.