If you are paranoid about things getting lost in transit on the way to the lab, save up your shipping of film until you get to your next major city, and then find the FedEx office and ship it back to the lab FedEx. Sure it costs more, but in the scheme of things, plus the absolute un-repeatability of what you're doing, what's a couple hundred dollars in shipping fees in the grand scheme of things? I don't know about photo labs between Mexico and Argentina/Chile/Brazil - there may still be some, and they may be good or may not. But certainly they still exist in cities like Santiago, Buenos Aires, Sao Paulo, Rio and Brasilia. There are some big camera stores in those cities - I'd go in and ask if they know of any that they could recommend. When I was in Buenos Aires a few years ago, there were still a number of 1-hour/next day photo labs doing fairly decent quality work. I had one issue with one that I used, but it was more a customer service thing than anything else: their machine dorked up a couple frames on one roll. This sometimes happens, even in well-run labs - I understand, as I used to work in a well-run minilab. The annoying thing was that they tried to blame it on my camera. I've been around the block enough times and put enough thousand rolls through cameras to know when it's a camera problem and when it's a lab problem. I know this is hardly a confidence-building story about the quality of mini-labs in South America, but my point is that A: the problem I had there I could just as easily have had here, and B: out of nearly 20 rolls I shot in twelve days, to have one roll with a couple of bad frames is not horrible. I would definitely ship the E-6 back to a lab here in the US, process the C-41 locally, and process the b&w yourself. Since you'll be traveling with your own vehicle, transporting chemistry will not be a problem. To save on weight and space, I'd try to use developers and fixers that can be mixed from powder, and just use a water stop.