mr moto, I bought a small guitar (but not the backpackers size) in Mexico for similar reasons - something to keep my mind from going mushier than it already is, and I am having fun learning how to play. I have a soft case, over which I put two garbage bags, one from either end to protect from water and dust. Over that two more bags, the big burlap ones (mine were from 20 kgs of carrots). This budle I wrap with one bungee cord.
This whole assembly is bungeed with two cords to the back of my dry back, which in turn sits just behind me on the bike.
It can occasionally be a pain to unload, load, etc, but generally, it has been good to have along. If I was a better player, I would learn more of the local songs and lyrics. Its a good conversation piece here in South America, and many people can play, which is great for striking up conversations. I would consider a smaller, backpacker style if I were to do it again.
Cheers,
Rene
www.renedian.com
[This message has been edited by Rene Cormier (edited 10 January 2005).]