At age 14, Valenzuela came back to the United States where he began working with quarter horses, then launched his career as a jockey at a racetrack in Tucson, Arizona.

He eventually began riding in California and came to national prominence as a jockey competing for the American Triple Crown of Thoroughbred Racing.

Leading up to the 1958 Kentucky Derby, the California horse Silky Sullivan received much publicity for his habit of coming from very far behind to win races.

On Kelso, Valenzuela won twenty-two important graded stakes races, passed Round Table to become the No.

Seventy-four-year-old Ismael Valenzuela died on September 2, 2009, and was buried in the Live Oak Memorial Park Cemetery in Monrovia, California.