Diaz was born and grew up in Washington Heights, Manhattan, the son of Cuban-born parents. In 1994, Diaz landed his first speaking role as “Spike” in Boaz Yakin‘s Fresh. From there he began working on Party Girl as “Leo”, Parker Posey‘s roommate. His next role was a drag queen (“La Miranda”) in Nigel Finch’s Stonewall. In 1996 Díaz worked in Jim McKay‘s Girls’ Town as “Dylan. After Girls’ Town, Diaz appeared in I’m Not Rappaport.
Diaz played “Paco de la Vega al Camino Cordoba Jose Cuervo Sanchez Rodriguez Jr.”, a high school gang member in High School High. He later appeared in Freeway as “Flaco”, another gang member. While in Los Angeles, Diaz did guest spots on ER and Party of Five.
After finishing work on the west coast, he traveled back east to shoot Brian Sloan‘s film I Think I Do playing the stoner “Eric”. A similar role then opened for Díaz; he scored the role of “Scarface” in the film Half Baked, on the set of which he met Dave Chappelle who later cast him in several episodes of Chappelle’s Show. In 1999 he landed a non-speaking role in 200 Cigarettes, and went on to act in Ethan Hawke‘s directorial debut Chelsea Walls and Just One Time, where as secondary characters he and Jennifer Esposito provided what little “comic spark” existed in the film.
Díaz played Guillermo García Gómez, a drug dealer/trafficker, in seasons 3-6 of Showtime‘s Weeds. In 2009, he started on the NBC series Mercy, where his portrayal of the gay nurse Angel received negative comments on forums for being too flamboyant. He co-stars in the thriller film Exquisite Corpse.
In 2010, Díaz was cast as a Latino gangster named Poh Boy in Cop Out, after previously portraying several Mexican thugs (cholos). When asked about about being typecast, he stated “I [used to worry], but not really anymore. Now I’m just grateful that I’m working. I try to make everything different.”
Diaz is openly gay but told Out magazine that the fact that he grew up in a rough neighborhood where he hid his orientation, “That facade of being somebody I’m really not just to protect myself definitely helped with acting.”