As a songwriter, Valenzuela has written or co-written Gin Blossoms songs including "Til I Hear It From You," "Follow You Down," "Mrs. Rita,"[2] "Until I Fall Away" and "As Long As It Matters."

[4] By 1989, the Gin Blossoms were fully up and running and released their first album, Dusted, with Hopkins serving as the principal songwriter but with Valenzuela contributing four tracks.

Some of its songs – "Lost Horizons," "Hey Jealousy" and "Found Out About You" – reached a wider audience when included on the band's major-label debut, 1992's New Miserable Experience.

All Music said the album was "filled with chiming guitars, sweet melodies, and simple, catchy hooks, as well as a sturdy grasp of traditional pop/rock songwriting that results in a number of gems.

Subsequent Gin Blossoms albums Major Lodge Victory (2006), No Chocolate Cake (2010) and Mixed Reality (2018) produced songs such as "Miss Disarray," "Learning the Hard Way" and "Heart Shaped Locket."

In addition to his work with the Gin Blossoms, Valenzuela has been active as a solo artist, session player, producer and composer for movies and television.

[9] Valenzuela's work for film includes the song "Screwed Up,"[10] written with Susan Sandberg for the Farrelly Brothers' 2007 remake of The Heartbreak Kid.

In 2022, Valenzuela was touring with the Gin Blossoms as the band was marking the 30th anniversary of the release of New Miserable Experience and was performing solo shows in the Phoenix area.