I'd say your previous mixes/ productions would be of most interest, but bringing a written document of anything you'd like to show off and not forget about wouldn't be a bad idea.
Maybe that was a joke, but from personal experience, it helps if you say you are willing to do any dirty work they need you to do...clean the bathrooms, make coffee, sweep up...it sounds shitty but they'll usually let you do alot of studio work as well.
It kind of makes sense, why should they have to do it when they have interns that can? Some studio owners get turned off by interns that make it clear they don't clean or whatever...its like being a Freshman in high school all over again; sometimes you have to pay your dues before you get respect.
Sounds like shit, but thats what alot of studios in the US are like.
Congrats man! Interning at a studio can be a priceless learning experience, even if you wouldn't get to fiddle around with the equipment that much. Just observing the pros do their thing is good education