We've always been assigned to the rear MDR. And except for one time, at a table along the panoramic rear windows. Great view!
It could be that we have always had a cabin toward the rear of the ship, going by some odd-rule that the front 1/2 of the ship tends to be assigned the mid MDR and the back 1/2 of the ship tends to be assigned to the rear MDR.
Though, we have always booked early too. So, maybe that's why we get the rear MDR?
From M&M, all you need to do is send your specific table request to John Heald, and he'll make sure you get that table (though IMHO, John doing such for some, but Carnival not doing it all passengers, isn't quite right).