Best route from Quito to Chile?

[IanC]

I'm in Quito at present, and not sure which roads are going to be best south, or perhaps there aren't that many options.

I don't have time for TOO many detours (taken too many already!), and want to take in most of the usual must-sees including:

Canon del Pato
Nazca Lines
Colca Canyon
Cusco & Machu Piccu
Lake Titicaca
La Paz?
Salar de Uyuni (not sure if Bolivia's complicated with bike?)

My immediate question is whether to continue through the Andes or drop down to Guayaquil? Andes seems obvious to me, but someone suggested the other.

Off in the morning, so last question first please!