Hi Katherine,
We stayed at Old Key West not too long ago, and I would definitely request a building based on my experience. Disney does their best to honor all requests, but unfortunately they can not be guaranteed. So this is what I would suggest and why:
For our trip with our young children we really wanted to be nearest to the hospitality house as possible, and thankfully we were! What I did not like about our room location (we were in building 12) was that in order to get to the hospitality house (main pool, restaurants and shopping) or bus stop, we had to walk across fairly busy parking lots, and there are no sidewalks available in this area.
So my suggestion would be to put a choice of two building numbers on your request, I would list buildings 62 and 23. They are both still close to the hospitality house, but you'll have nice sidewalks and crosswalks to get you there safely! Just as a side note, there are only three buildings that have elevators (62, 63 & 64) so if that is an important feature you might want to request an elevator building (or request to be on the ground floor).
If you haven't seen it yet, I suggest you check out the
www.allearsnet.com website, if you look at their accommodations section they have a bunch of great photos as well as a resort map.
Hope this helps, have a great trip!