What we found out several years ago (wow, 10 years ago - time flies) is that our taxi drivers didn't speak English, and our Spanish is not that great and I can't even make an attempt at Catalan!! So communication was a bit of an issue. Our hotel and the taxi stand at the airport helped get our driver pointed in the right direction.
The airport bus worked better. and now that we know how subway systems work (from "practice" in DC, London & Paris) I would do the subway to get to where I was going.