I see the # were recently replaced with No. with a reference to the manual of style.

I think the # still makes more sense for the infoboxes. The manual of style is more of a guideline, not a hard rule, and the examples used are more textual in nature. For example if you were writing it out in a sentence then No. makes more sense than #. However given the space limitations of an infobox, I think having the simple # is much better. It also isn't meant to be grammatically correct, it's filled with various symbols already and what not. And on top of that there's the consistentcy issue. At this point there are hundreds of thousands of college football related articles utilizing #'s for poll rankings. I'm not sure if breaking consistency is worth following the suggested style. I do think that the "No." style makes sense when used in sentences in articles though.