BootsnAll Insiders

I'd like to get on a bus in Mexico City or Tapachula and eventually end up in Colombia. Time is not a problem, but cost is. Has anyone done something similar?

I could use information on where to stop off, sights to see along the way, how to get around places where you can't go by land, and how long the toal trip would take if I didn't do any sightseeing.

Thanks