We did LA round to Miami did not bother with anything.

When it comes to travel Malaria is only one of the things to consider.
For travel anywhere(including europe) it is worth considering a basic set.
read up a bit on how the different inventions are transmited so you can ovoid getting things, even with protection you can still get ill.

Lots are blood or food related so if you don't do risky activities(injury) and are carefull with food the risks of some are very low when traveling by ship.

I also find it usefull to look at UK resources and US, they are sometimes give different advice.

For malaria have a look here
http://www.cdc.gov/malaria/risk_map/

This UK one has a good map of risk areas so you can follow your route also has info on the other risks.
start with panama malaria map.
http://www.fitfortravel.scot.nhs.uk/destinations/central-america/panama/panama-malaria-map.aspx