I guess I will have to dissagree, I always take gifts when I go. The times we have done land based Mexico trips and are on the beach we take things like ball caps. A couple of years ago a friend of mine was the city building inspector and he sent us to Puerto Vallarta with about 30 hats with names of various busnesses printed on them. We passed them out and one man said it was the only gift he would have for his son for Christmas. It was so humbling. We have taken tootsie pops, gum, tooth brushes, things from the dollar store like stickers, we have taken Taco Bell Dogs, and cheap and small toys, this may only work from the beach where you have time to sit and not at the port where you are being besiged by the selling masses. If you want to take something, see about one of the orphanges locally and see what the needs are.
Sometimes when we go, our dentist will send a box of toothbrushes and tooth paste to take down to the orphanage.
On a humorous note, those hats, we would see them all over town [ because of the logos ] and mostly they were on different heads, so no telling what they bartered them for, oh well, I still felt good