It's my first time on this message board, and I see this - excellent blog. Hope you have a great trip. Myself and some friends did a similar kind of boating trip in 2004, flying into the USA this week two years ago and finishing in Buenos Aires in July 2005.
Nicely pimped school bus. If my experience is anything to go by, you are going to have a fantastic time. Our escapades are on our website:
(protected by idiot-filter, you'd be surprised how many people can't get past the first page).
If there's anything you need by way of beta, contacts, Guatemalan mechanics, etc., drop me an email.