Most of the all-inclusives in the Cancun area you can also find on RCI extra vacations. That way you don't have to use up your deposit and no exchange exchange fee. The all-inclusive fee is the same either way. I myself don't like all-inclusive as it is so pricey and then your restricted to eating and drinking at the resorts restaurants, but I know that is not what you asked:ignore:
I have booked all-inclusives both ways through exchange(extra vacations) and also with travel agencies or travel clubs. If you plan on staying for 7 nites and can get decent airfare you will save several hundred dollars with RCI. If you only want to go for 4 or 5 nites it might be better to use a travel vender. Most of my experience is with the Palace group(Moon,Cancun,Beach,Sun) If the is the All-inclusive group you are looking at look around the Tug their are some owners that rent their weeks packages quite cheap I believe.