Stephen, my understanding is that Borja will carry BTC and exchange them for local currency in each country, using https://localbitcoins.com/. I guess it should be easier to find people who want some bitcoins in Africa than people who have them...

Western Sahara:

try contacting this hotel-
http://www.hotel-nagjir.com/contact.html

Nagjir Ville
Adresse : Place Résistance Làayoune.
Tél : +212 528 89 41 68/69
Fax : +212 528 99 09 82
Email : hotelna@hotel-nagjir.com
P.GPS : Altitude -27°9'0.40"N
            Longtitude -13°11'55.64W