What the @#!* do you need to drop off a letter for if you're physically stopping by? You are the LOCI.
Completely disagree with the above comment.
The person who gives the tour or meet with you might not be the one who have the decision power. And even if he does, he might forget about you in few weeks when it comes down to evaluate the waitlist. Giving them the letter will put something on your file and be there for the actual reviewers to see when/if they review your file again.
Don't listen to Ninja1. He's a clueless-UF-Hating 1L.