I am living outside Barcelona in a small city called Manresa. I took a Catalan course that was run by the ajuntament and was free. It was only neccessary for me to buy the books. So, when you get to the town you are staying in be sure to ask if it is offered. The govt here in Catalunya wants foreigners to learn this language to preserve ?their history and culture. So, be sure to inquire at the ajuntament/ayuntamiento.
Which language to concentrate on….Spanish, Spanish, Spanish…A native would kill me for saying so, but if you have studied Spanish before or atleast speak some, I think it is much easier to learn spanish first and you will pick up Catalan alon the way. Remember that EVERYONE speaks both Catalan and Spanish. So, it’s not like you will ever have a problem communicating if you do not speak Catalan. Once you can speak catalan or show them that you are attempting to adapt to their language and culture, you may be accepted by more people.
Good Luck to you.
Mike