Take your baby and have fun. I have traveled with my kids to Mexico since they were 3 months old and nothing bad has happened to them. If you are breastfeeding the baby will not have to drink the water! Dont bath the baby in resort water even though they say it is filtered and you will be fine. Drink only bottled fluids and dont eat any fruit that does not come in a peel...like dont eat fresh salads.
Despite what the other people have posted Mexico does have great healthcare. I had an emergency in both Cancun and Puerto Vallarta and recieved excellent care by AMERICAN trained doctors! And I was in and out in under an hour for under $100! Can't get that here!
LOL
Dont listen to all these doomsdayers!