Catalan is not going to be a problem. Most people in Barcelona has Spanish as mother tongue. Catalan is more popular in the countryside. The Catalan nationalism is everywhere in the public sphere (public administration, public schools, traffic) because of regional government in hands of Catalan nationalists/separatists. Fortunately, private companies have not that imposition, and commom sense rules: most things are in Spanish and English. Of course, some people -including myself- speak in Catalan with other people, but switch immediately to Spanish or English so no one feels excluded.
If you're thinking about investing in Barcelona, and having fears about the separatist movement: don't worry, it is not going to happen. In that regard Barcelona is pretty much like London: separatists are a minority, being the separatist power in the countryside. So before the Catalan region of Spain becoming independent, Barcelona would remain as part of Spain (in the improbable case of all Spanish citizens agreed about allowing a "Clarity Act" like in Canada, so if Spain could be divided, any separatist region could be divided as well -that would be going "nuclear" against separatists that consider the Catalan region of Spain as "indivisible"-). So independence chance is 0, in my opinion. I hope Catalan nationalism will reduce its influence once their leaders pass through the court (corruption cases), and everything gets back to normal, with bilingüism/trilingüism in the schools and public administration, instead of current de-facto Catalan monolingual stuff in the public sphere. If after that you still have doubts, invest in Madrid first, and think about Barcelona once the political scene gets more rational (I love Barcelona, don't get me wrong).