That's a very good question, and one I hadn't even considered. I just went on the website for the Centers for Disease Control
http://www.cdc.gov/travel/
then went to the drop-down menu and chose Central America and Mexico. Besides the list of shots, there is also good information about other ways to stay healthy. Here are the recommended shots:
CDC recommends the following vaccines (as appropriate for age):
See your doctor at least 46 weeks before your trip to allow time for immunizations to take effect.
Hepatitis A or immune globulin (IG).
Hepatitis B, if you might be exposed to blood (for example, health-care workers), have sexual contact with the local population, stay longer than 6 months, or be exposed through medical treatment.
Rabies, if you might be exposed to wild or domestic animals through your work or recreation.
Typhoid, particularly if you are visiting developing countries in this region.
Yellow fever for travelers to Panama who will be going outside urban areas.
As needed, booster doses for tetanus-diphtheria and measles. Hepatitis B vaccine is now recommended for all infants and for children ages 1112 years who did not receive the series as infants.