The open top buses do 4 interchangeable trips, for about €25 / person you can jump off and on depending where you want to go. The down side is you see alsorts of crap and are stuck in traffic. The answer and the far cheaper option by far is to plan where you want to see and get taxis, most drivers speak at least some English and will give some inside info on the places. Get to the Segrada Familia if you're going, early as the queues go round the dam thing.. KFC is bloody expensive but the fish market up the Rambla is worth while, the cheaper restaurants are on the streets running paralell to Las Ramblas. A trip round the Camp Nou is worth it and so is a wander round the sounvenier shop. Watch your pockets, seriously and just take what you need. It could still be a touch nippy if there's snow on the Pyrenees so, as my mum says, take a pully.