As far as I know and according to their official site, only three games take place that month at the Camp Nou: Barça-Deportivo de la Coruña (10/03/13), Barça-Milan (12/03/2013) and Barça-Rayo Vallecano (17/03/2013). We are talking 20-80€ for the Rayo Vallecano, but 80€-160€ to see the Milan (that's expected to be a very good game, in case it wasn't obvious); there aren't many seats left, so if that's when you are going, buy the tickets now before it's too late!
About the city itself, well, obviously the two most visited landmarks are the Camp Nou (AKA the Catalan Mecca) and the Sagrada Familia (make sure to get inside, by the way, it's definitely worth the standing line); aside from that, you want to visit the "Barri Gotic" (old city center, beware the pickpockets), las Ramblas (beware the pickpockets there too) and "Passeig de Gràcia" (the most recognizable XIXth century Barcelona), anything else signed by Gaudi (at the very least you've got the "Parc Güell" left, that isn't negotiable). Then it depends on how much time you've got and the kind of things that you want to see, but the Port is nice and there's plenty of thing to do there; so is the Tibidabo (one of the hills that surround BCN), which among other things holds a 112 year old amusement park; Montjuic (with, among other things, the "Palau Nacional", AKA Catalan National Art Museum).
And in case you didn't know, most people only grudgingly speak Spanish in Barcelona, they rather speak Catalan here. On the other hand, Andalucian accent is pretty rough too, so if you were planning to improve your Spanish, tough luck
Where to Andalucía, by the way? Córdoba, Sevilla, Granada...?