I flew into La Paz, had a five hour layover, then flew to Sucre. Overnight in Sucre, moved to Potosi for two nights, then to Uyuni, which I enjoyed by the way...if you go there you got to eat at the Minuteman Pizza...then did the three nights/four day tour using Quechua Connections.
I was there in mid-April '14, very little water on the salt flats, brilliant blue skies, perfect weather. Awesome food, great driver. It was ALL good!
Regardless what you decide on, I am sure you will find it to be spectacular!
