I upgraded from an ALON last December to the concierge floor (for three rooms!) with no problem, but the hotel was at about 50%. Call about one month ahead of time and ask to have the request for an upgrade put in your record.
I highly recommend the upgrade if you can get it as the concierge level has a free breakfast every morning and a cocktail hour in the afternoons. As I had the entire family with me (see three rooms above), this was invaluable as everyone would meet up for breakfast and then again for the cocktail/soda hour.
I am assuming you mean Diamond status versus Platinum (?). If there is any way at all you can get there, please do. Diamond members (and this applied to all the rooms) have free access to the spa daily for workouts/exercise classes and hot tub/sauna (non-Diamonds pay $10/person/day if I remember correctly). The amenities for the higher level VIP at this facility are fantastic - we had a one of our best vacations ever. The only downside was the $6 beers at poolside, the bar tab can get a bit shocking by week end :-) Be sure and do a snorkeling trip as well if you have time (the concierge will even set it up for you) - good luck.