In 1997 he opened Sol y Luna on 7th Avenue South, featuring Mexican tapas specialties. He later opened Los Angeles, which featured Caribbean and Latin dishes. In 2004 he opened the first location of Cantina in the Martin Biscuit Building at Pepper Place. That concept has since developed into a chain, with locations on Cahaba Valley Road and the Patton Creek Shopping Center, as well as in Montgomery's Alley Station.
Castro died in 2011 after suffering a heart attack.
- Carlton, Bob (July 18, 2011) "Birmingham restaurateur Guillermo Castro, who owned Sol y Luna and the Cantina, dies at 52." Birmingham News