Guillermo is a writer of drama and fiction as well as a director, dramaturge, translator, and actor. He is the recipient of a Governor-General’s Award for Drama for his play Fronteras Americanas et a remporté quatre fois le prix Chalmers pour une pièce canadienne. Son œuvre, qui comprend Feast, the Governor-General’s Award shortlisted Noam Chomsky Lectures (avec Daniel Brooks) qui a été présélectionné par le Gouverneur général Adventures of Ali & Ali (avec Marcus Youssef et Camyar Chai), A Line in the Sand (avec Marcus Youssef), Our Heart Learns, bloom, et Another Country has been recorded, anthologized, translated into Spanish and Italian, produced in Europe, Australia, and the US, and is studied in Latin America, Australia, Europe, and North America.

A director and actor, he has worked at theatres across Canada, and has also translated plays by Federico Garcia Lorca and Ximena Escalante.

His newest work, Versus (co-created with Adam Lazarus and Ann-Marie Kerr) will premiere in Toronto in early 2026.