You're using linear indexing to index into a 2d cell array, so assuming that n is the number of rows, you're only indexing the first row. Use row, column indexing and index both columns in your loop. That is replace your fprintf with:
fprintf('%d %s %d\n', k, BalloonCellArray{k, 1}, BalloonCellArray{k, 2});
Note that using expansion of cell arrays into comma separated lists, the above can also be replaced with:
fprintf('%d %s %d\n', k, BalloonCellArray{k, :});
If you do use that second, you'd better put a comment explaining what's happening (by linking to the above doc for example).