That's right, we do expect dinner ... haha, it is a good deal. But, I think it is a way to force you guys to try some awesome New Orleans food.
I've hosted a bunch of people and most take us out to dinner and some don't, and that's fine, I don't care. I think a thank you note is a nice gesture, but again, not a big deal.
The best thing to do is make it as easy as possible on your host: take a cab to their place, ride with them in the morning for the interview, don't make a mess, and take a cab back to the airport. Doing the above would be thanks enough.