Here in Canada we have been seeing ads to have Hepatitis A and B shots if visiting the Caribbean, especially beaches in Mexico. It seems such a shame to have them for the few hours there...have you heard about this? My son would freak if I said needle, but are they available for children too?
Check out <http://www.cdc.gov/travel> for the latest travel health information. I spent a week in Playa del Carmen in November and I wasn't aware of any issues related to hepatitis there. We came back healthy.