Do not miss Colombia!
We are travelling this proposed route in reverse (Mexico to Chile) at the moment, and are currently in Peru.
We have been to every country so far, and Colombia is easily our favourite.
I'm planning to go back already, actually considering looking for work out there, as I met a few people from the UK working over there in Cartegena and Bogota.
Check out my travelog if you want some more info:
http://www.travelpod.com/members/dospollosWe decided to fly from Panama City to Cartegena, but you can go overland if you fancy a days walk along a beach. Check the current status before you do it, that region has its ups and downs

The other option is to take a boat, which works out more expensive than flying sometimes, and can take up to a week with stopovers, but you do get the opportunity to check out the San Blas islands of Panama if youre lucky
