For anyone who wants to do the same, insanely awesome thing that I’m doing: here are some links I collected over the last few months that helped me a lot:
Budget tips for travelling in the Caribbean: http://koucou.com/c/budget-tips/
Backpacking around Central America: http://www.lonelyplanet.com/thorntree/thread.jspa?threadID=1396212
Ferries in the Caribbean: http://www.lonelyplanet.com/thorntree/thread.jspa?threadID=1385677
Sea Transportation in the Caribbean: http://koucou.com/c/budget-tips/transportation-sea/
Tips for bus travelling in Central America: http://gocentralamerica.about.com/od/gettingtherearound/a/Bus-Travel-In-Central-America.htm
Central American Travel for Students and Backpackers: http://gocentralamerica.about.com/od/studentsbackpackers/Central_America_Travel_for_Students_and_Backpackers.hts
Forget anything else then LONELYPLANET for Central America. In Cuba there is a Petit Routard but I didn’t really like it.