For food, wander around the Santa Cruz barrio and stop at any of the myriad tapas bars. The closer to the cathedral you are the more expensive it will be.
A word of warning – as soon as you sit down, they’ll bring bread or breadsticks to the table. If you don’t want them, say so as you will be billed for it otherwise. also always check your bill, because we noticed stuff we hadn’t ordered was frequently on ours.
Stuff to do ? The bull ring tour is excellent and the open top bus is a great way of getting around, hopping on and off. A visit to the footy is quite an experience.
I’ve been to the city twice and my favourite way to spend the time is just to wander around slowly getting fed and watered – marvelous.