On September 18, 2009, Galarza won his first professional title, defeating Joshua Allotey to become the first interim light welterweight champion of the North American Boxing Organization.

Galarza learned the basics of the sport in a gym established in Collores, a barrio located in the municipality of Juana Díaz, considering Félix Trinidad his inspiration within the discipline.

[10] In that year's International José "Cheo" Aponte Tournament, Galarza advanced to the semifinals, but lost to Myke Carvalho by points, 14:12.

[11] On October 3, 2005, Galarza won the light welterweight (64 kg, 141 lb) silver medal at the Pan American Boxing Championships, only losing to Inocente Fiss by referee technical decision (RTD) in the final.

[12] Galarza participated in the 2006 Central American and Caribbean Games, where he debuted defeating Luis E. Grajeda Ozaeta of Mexico by points (8:6) in the 64 kg division.

He was unable to compete in the 2006 Campeonato Nacional Isaac Barriento de Boxeo Aficionado tournament due to an arm injury.

[17] Galarza, along twin brothers Carlos and Juan Velázquez, was one of the national team's boxers that decided to become professionals before the 2007 Pan American Games.

[24] In the undercard of last 2008 episode of ESPN2's Wednesday Night Fights, Galarza defeated Devarise Crayton by knockout at the 2:57 mark of the second round.

The card was held at the Juan Pachín Vicéns Auditorium in Ponce, marking the first time that Galarza performed in Puerto Rico since becoming a professional.

[32] Galarza's next fight was against Roberto Acevedo, performing as part of a card titled "Boxeo de Campeones" which was presented by Universal Promotions.

Prior to this fight, the negotiations with Acevedo's team stalled and Javier Bustillo, who organized the event, contacted a second rival to fill the vacancy if his offer was refused.

[35] The fight featured exchanges from both pugilists, Galarza used his offensive to weaken Allotey with left hooks and uppercuts, moving the punches towards his opponent's head as the contest advanced.

[38] His first contest of 2010 was scheduled for January 29, fighting against former International Boxing Organization super flyweight champion, Ilido Julio, co-headlining a card held at UIC Pavilion along Donovan George.

[40] His next participation was in a preparatory contest against Miguel Casillas, held on March 12, 2010, as part of ESPN Deportes' Viernes de Combates series.

In the third round, he pinned Casillas to the ropes and connected several consecutive punches, the attack continued without response and the referee stopped the fight by technical knockout at the 1:27 mark.