I agree with Alvaro. My advice is that first you learn Spanish and secondly Catalan if you want to stay in Barcelona (or region) for a long time, almost for a job.

In Spain only speak  Catalán in Cataluña but there are a lot of people living there that isn´t "catalanes". So if you speak catalan only understand you the "catalanes" but if you speak Spanish, all people in the Spain understand you because all person in Cataluña know Spanish although they (catalanes) don´t recognize

Quite rare to see an English person know four languages. :) 

In my opinion, if you are going to live in Barcelona for a long time, you might learn catalan, but if you will be there for short time, I am of the opinion that you must improve spanish rather than catalan, because most people are very polite and if you speak them in spanish, they will reply you in spanish too. :)