Lisbon is relatively inexpensive by European standards and a quick 1hr 20min flight from BCN. It has an extensive public transportation system that makes it easy to get around and it's a very laid back type of atmosphere.

If you go, make sure you take the train along the coast (30 mins) from Lisbon to Cascais, a small former fishing village that is now a bit touristy but with a "drinking square" in the middle.