i'm going to go out on a limb here...i think if you can, it is best to have your guests stay in one spot. i think it really dilutes the experience of a DW if they are all staying in different areas. one of the main reason we had a destination wedding was so our friends and family could spend time with us and each other. it was such a great way for us all to get to know each other better. my parents and his parents are so fond of each other now.
we loved having our meals together, lounging by the pool together, the ladies doing a spa day together, the younger group went out together.
then throw in the fact that you are trying to get a large group of people together and have them navigate around a town that they are unfamiliar with and do not know the language, i think you are causing a stressful situation. in an ideal situation, you would have all those details taken care of for them so they really just need to show up. Keep in mind transportation can get expensive....the $40 a day they spent on cabs could have gone to a better resort.
i think for anac, your family speaks spanish so it doesnt really apply. sherri and tammym your groups are so small it is different as well...
i really think if you are thinking a group of 20 or more it is just better...or at least have them only stay at 1 or 2 resorts that are fairly near each other.
my 2 cents.