I was on the Summit to Puerto Limon and Panama in January. I donate blood on a regular basis, but cannot donate for one year because the area from the port to town/any excursion is considered the Malaria area. I don't think you will need any vaccinations or such, but be cautious as you would anyway.
I enjoyed the banana plantation in Limon, but many LOVED the canals!
PS. If you get a chance say hello to two of my favorite bartenders (one is asst bar manager now): Jose Yanez and Hector Canon - both are on Mille now, but may be on vacation by then.