A historical person of that name was Governor of Sepulveda in 1086. There is no documentary evidence tying him with Alvar Fanez or San Esteban de Gormaz.
And Felez Munoz went his way towards Valencia; and when he came to Santesteban he spake with Diego Tellez, who had been of the company of Alvar Fanez, and told him of what had befallen.
So he told them the name of the good man with whom he had left the dames, and the place where he dwelt, and also how he had spoken with Diego Tellez at Santesteban, and then they parted.