Sanchez was born in 1957 in Mexico City, to parents of German and Cuban heritage, and emigrated to the United States in 1962. Sanchez studied writing at the Fine Arts Work Center in Provincetown, Massachusetts, under Michael Cunningham, Richard McCann, Allan Gurganus, Peter Ho Davies, Michael Klein, Elizabeth McCracken, and Jacqueline Woodson.

Sánchez’s works explore themes of love, friendship, family, coming of age, and gay, bisexual, and questioning youth. His first novel, Rainbow Boys (2001), was selected by the American Library Association (ALA), as a “Best Book for Young Adults”. With the novel’s debut, Publishers Weekly (PW) Magazine deemed Sanchez a “Flying Start”.

Two sequels, Rainbow High (2003) and Rainbow Road (2005), complete the Rainbow trilogy, portraying the coming of age of three gay and bisexual teenage boys. Both novels were honored as “Books for the Teen Age” by the New York Public Library.

Sánchez’s novel So Hard to Say (2004), about a group of 13 year-olds, won the Lambda Literary Award for Children's and Young Adult literature. Getting It (2006) won the Myers Outstanding Book Award for Human Rights and also second place at the 2007 Latino Book Awards for Best Young Adult Fiction in English. The God Box (2007), focuses on the conflict and friendship between two Christian teenage boys, one openly gay and the other struggling to accept his sexuality. His novel, Bait, about a teenage boy struggling with secrets from his past was released in June, 2009.

Additional works by Sánchez include his short story, “If You Kiss a Boy’, which appeared in the anthology 13: Thirteen Stories about the Agony and Ecstasy of Being Thirteen (2003), edited by James Howe.

Although Sanchez's novels are widely accepted in thousands of school and public libraries in the U.S. and Canada, they have faced a handful of challenges and efforts to ban them. Linda P. Harvey of Mission America in Columbus, Ohio, targeted Rainbow Boys in her essay “The World According to PFLAG: Why PFLAG and Children Don’t Mix Unless you happen to like child abuse” (sic). The book was also challenged by citizens in Owen, Wisconsin, but ultimately retained by the Owen-Withee Junior and Senior High School, although the superintendent suggested creating a policy of requiring guardian permission to check out the book (ABFFE). In addition to the Wisconsin challenge, the book was also challenged at the Montgomery County Memorial Library System in Montgomery County, Texas (Doyle 6). The ACLU of Texas also reports that Rainbow Boys was challenged in Texas during the 2004—2005 school year (ACLUTX 30). One of the most recent challenges occurred in 2006, when the Webster, New York Central School District removed Rainbow Boys from the summer reading list. After numerous protests from students, parents, librarians, and community members, the book was placed on the 2007 summer reading list. In Canada in 2008, the superintendent of Schools for Charlotte County, New Brunswick canceled plans for Sanchez to speak to students in the high schools "after a few parents objected." However, after hearing Sanchez speak at a presentation, he said he would recommend the gay author as a speaker. "Oh absolutely. Definitely. Now that I've heard him, he's wonderful. But I needed to hear that message."