Garza was born into the military family of retired United States Air Force Staff Sergeant Arthur and Maria D. Garza and traveled extensively in his early years.^[1] In 1967, the family returned to its Westside San Antonio home.^[1]

Garza graduated in 1973 from John F. Kennedy High School in the Edgewood Independent School District of Bexar County.^[1] He attended the University of Denver in Denver, Colorado, from which he received his bachelor's degree in Mass Communication in 1977.^[1] He married Debra A. Garza in 1980 and has reared five children, John Zachariah, Jacqueline, Isaiah, Rebekah and Hannah.^[1]

Garza has had a lengthy career in housing and real estate; he has held several executive positions in his business and sales career which dates back to the 1980s.^[1]

Garza's District 117 is among the most rapidly growing parts of Bexar County.^[2] It encompasses the far west and southwest portions of Bexar County, including the cities of San Antonio, Helotes, Von Ormy, Lytle, and the unincorporated community of Macdona. The district also includes Lackland Air Force Base, University of Texas at San Antonio, Texas A&M University–San Antonio, and Palo Alto College.

Garza was defeated in the 2012 general election after only one term in office by the Democrat Philip Cortez, who regains this seat in 2017 after a two-year absence. Garza subsequently failed in a comeback attempt in the March 4, 2014, Republican primary for House District 117. He lost the nomination to Rick Galindo, a San Antonio businessman who received 2,372 votes (64.6 percent) to Garza's 1,300 votes (35.4 percent).^[3] Galindo then narrowly unseated Cortez in the November 4 general election. In 2016, Cortez regained the position by defeating Galindo.

Garza was one of forty freshmen legislators in the 82nd Texas Legislature. He was one of six Hispanic Republicans serving in the House from 2011 to 2013 and was a founding member of the House Hispanic Republican Conference.^[6]

Garza served on the House committees of Business and Industry and Land and Resource Management.

Garza in his one term in office authored or co-authored more than thirty-five bills dealing primarily with property tax reform, rural and suburban water rights, election integrity, greater accountability in government, and home owner association reform.^[7]

In the general election held on November 8, 2016, Garza ran unsuccessfully for the Bexar County Precinct 1 commissioner's post. He was defeated by the incumbent Democrat Sergio "Chico" Rodriguez, a brother of former U.S. Representative Ciro Rodriguez of Texas's 23rd congressional district.