Rafael Uscha, well known by everyone in the village of Licto, 15km south of Riobamba, is the salesman for the Cooperativo de Guias de Guargualla (natives). In 2005 he was reachable @ 03-949-552.
Marco Cruz (also metionned in one of the posts here) is a very skilled mountain guid based close to Riobamba. I believe he is one of the rare Ecuadorians being UIAGM certified (formé à l'ENSA de Chamonix). Check Expediciones Andinas
. Price wise: $$$$$
A very professional guiding agency downtown Riobamba is Alta Montana, avenida Daniel Leon Borja 35-17 y Diego Ibarra (phone in 2005: 295-06-01, fax: 294-22-15, e-mail: aventurag(at)laserinter(dot)net). They also run a hut, Stacion Urbina 23km north of Riobamba on the flanks of Chimborazo @ 3650m.
Salutations des cousins d'Amerique