Our belief is always cover yourself. We got hep shots... which is something that is a good standard if you're planning on traveling to unsure areas. We also got the chloroquinine (I think) pills for malaria. Did that cause we spent time inland.
We had no problems with bugs at all... probably partially cause of the time of year we visited. We also ate, drank and played merrily and had no problem with the water. Bought bottled water to make sure we could always stay hydrated by having something to drink.
First timers impression? Absolutely no problems with any physical issues. And what a GREAT place to visit!
P.S. We did our first trip the last two weeks of October last year. Wilma was getting ready, and then actually blowing through, while we were there. I think this might have had something to do with the low bug count at the time.
Safe, wonderful and absolutely incredible trip! Go for it!!!!