He returned to Puerto Rico in 1921 to continue his mechanical engineering studies at Recinto Universitario de Mayaguez.
In 1932 he returned to Ponce with his wife Celia Gómez and their newborn baby to work in the private sector.
[9] In 1935 he returned to San Juan where he was briefly employed in the Puerto Rico Emergency Relief Administration and later as construction inspector at Casa de España.
[10] Stunned by the death of his father in January 1936 and that of Pedro Adolfo in October of the same year, Mendez Mercado returned to Ponce in 1937, where he remained until 1941.
"from his drafting table, in the 56 years he was active practicing architecture, he forged ideas that, in one way or another, have affected the development and memory of the Puerto Rican people.