@OP: If you're flexible re travel dates use a service like ExpertFlyer to check for available upgrade inventory before you purchase your tickets - there may be availability there for the taking on some flights on/around the dates you are looking at .

If space is available you can call AA immediately after purchasing your itinerary and grab the upgrades there and then. Being on the waitlist means you may not clear the upgrades until the day of travel or not at all if you don't have status