[3] He was spotted playing for Santa Clara by scouts from the West Ham United International academy and moved to England in 2009.

[3] He made his official debut on January 5, 2014, for West Ham in a 5–0 loss against Nottingham Forest at The City Ground in the third round of the FA Cup.

[8] Lletget made his first start with the first team on June 13 against Columbus Crew, in a match where he scored the opening goal of the game, which was also his first for the Galaxy.

[12] In the 2016 season, Lletget scored a brace on June 14, 2016, against UPSL side La Máquina FC in extra-time of the Fourth Round of the U.S. Open Cup.

[13] Lletget again scored a late brace in the U.S. Open Cup, helping the Galaxy move to the semi-finals after 4–2 victory over Seattle Sounders FC.

[16] On March 9, 2022, Lleget scored the game winner in the Revolution's quarter final 2022 CONCACAF Champions League matchup against Pumas UNAM.

On January 6, 2017, for the first time, Lletget was called for the United States national team (USMNT) by coach Bruce Arena.

[21] On March 24, 2017, Lletget scored his first goal for the United States men's national team in a World Cup qualifier against Honduras.