If you’re willing enclose the whole thing in the link, you could just change: <?php comments_number('no comments', 'one comment', '% comments');?>
to: <?php comments_number('There are no comments on this post.', 'There is one comment on this post.', 'There are % comments on this post.');?>
Assuming you thought of that and found it inadequate, how about get_comments_number? It’s not documented in the Codex, but the code of the comments_number function (which can be found here) calls it and it seems to be returning an integer.