Master, I would advise against skipping the Hep-B. Hep-B transmission is not entirely understood, and though Nica is an amazing place, the infrastructure reminds me of my worst childhood forts.
When I went I got both Hep vaccines and typhoid. The malaria pills are unnecessary unless you are planning on spending a ton of time in the jungle. They are not good for you, and when you get down there you'll find that most foreigners and Nica's with 'good' medical access do not bother. Get the Tetanus booster if you have the cash, I saw a snooty Israeli girl get attacked by a dog (hilarious) and she had to get one afterwards.
Buy the Ciproflaxin (anitibiotic to help stem the flow from your ass), and Diazepam (Valium) if you want, when in Nica. No prescription necessary and it's cheaper.
Though Lee's advise is spot-on, I ate and drank nearly everything when down there (and yes I payed the price). Still can't help but recommend the Carne Asada from the street vendors behind the cathedral in Leon, if you make it up North.....