Barcelona is fantastic. Good beaches (which you will probably still be very pleasant during October), brilliant architecture, loads of history and culture, fantastic food (especially the local paella!) from hundreds of great restaurants and quiet little bars (or noisier ones if you prefer!).
It's also cheap to get to, with easyJet having flights into the wonderfully named 'El Prat' airport (which is also served by BA, Monarch and bmiBaby), and Ryanair both Girona and Reus (which are both about an hour from Barcelona on the direct bus services). Within Barcelona, there's a cheap, clean, efficient and fully-integrated public transport system, making it easy to get around.
http://www.barcelonaturisme.com/
Chris