First I doubt Zunino lasts until pick 13, and second I think people are way too high on him. He's essentially the same prospect as Matt Wieters was. His ceiling is great but the defensive aspects of the position can take a lot out of player, and as he gets to the majors he'll be more focused on defense then his bat.
I'd personally take Byron Buxton if he's there at 13. Further away but considering it's your second pick it won't hurt you.