What to learn on a 8-month roadtrip?

By the end of April me and my girlfriend will be on a 8-month road trip that will take us from Amsterdam to Cape Town.*

During those eight months I would like to spend time on learning a new software development skill. At the moment I do most of my work in PHP and ruby.

What would you start to learn? Internet access is most likely limited and/or slow.

*the exact route is unknown right now but we intend to roughly follow this route: Amsterdam, Istanbul, Tehran, Amman, Cairo, Nairobi, Cape Town.