The Sahara along the Atlantic coastal road is 2000 km long, between Guelmim and Nouakchott. The road is a pleasure to ride, I was in the desert during March 2013.
More details, stories and pictures on: freewheely.com/category/sahara/
Where to find food and water on the road: freewheely.com/2013/04/food-and-water-to-cycle-across-the-sahara-desert/
Main cities : Guelmim, Tan-Tan, Laayoune, Boujdour, Dakhla, Nouadhibou.