DH & I went on a medical mission to Jamaica 10 yrs ago

I know what you're thinking--
Jamaica, what kind of mission is that! We stayed in Montego Bay at a little run-down motel and commuted by bus 2hrs up into the mountains every day to deliver meds, doctors, nurses, dentists and opthamologists to some very isolated people. While the families waited in line for hours to be seen, some of our youth entertained the kids with Vacation Bible School activities, puppets, songs and games.
It was the most rewarding "vacation" we've ever been on. It totally changed my outlook on my own life and the lives of people in the Caribbean. I had never seen real poverty before--prepare yourself for that. DH helped the dentist--they pull teeth there rather than do preventative care(too expensive for most people). I didn't see a single adult with a full set of teeth.
Be very aware of how you dress. In a lot of central American/Caribbean countries the dress is a little more formal. You don't see women wearing pants and sleeveless shirts in Jamaica, unless they are very young. Spaghetti straps and shorts would be offensive to nearly all the population and the men might get the wrong idea entirely.
Be careful what you eat and drink. We brought our own water, but a helpful local added some local water to our container when he saw it running low. As a result me and another worker came down with vicious stomach cramps, vomiting and diarrhea. Unfortunately, as the only nurse in my group I had to go up the mountain anyway. I thought I would die, and I lost 15lbs that week.
Be sure you have some kind of insurance because unlike the U.S., they arent required to treat you regardless of abilitiy to pay. One of our doctors suffered a kidney stone and had to be transported down the mountain to the ED. The FIRST QUESTION they asked was if he had a Visa credit card.
I never saw a parent smack a kid or speak harshly the whole time. I also never saw a single toy, not even a ball. Some of us brought crayons and coloring books to give to for the kids waiting in line and they were snapped up quickly. If I were doing it all over I would pack only half the clothes and more art supplies/toys(crayons, paper!, scissors, nerf balls, flattened soccer balls)
I hope you go on a mission trip. Your eyes will be opened not just to what you can do for them, but what they will do for you. It is a grueling experience and disorienting at first. But it will leave you breathless for more. I miss going on mission. Since DH has been so ill it has been impossible, so now we supply money for others to go.