He holds a Bachelor's degree in Natural Science with a Major in Biology from the University of Puerto Rico in Río Piedras.

Dalmau began his political career as a teenager when he served as interim president of the Popular Youth in Caguas.

He was elected to the Senate of Puerto Rico on November 7, 2000, at the age of 34, representing the District of Humacao along with his running mate, Sixto Hernández.

While a minority in the Senate, presided by the NPP's Kenneth D. McClintock, his delegation represented the executive branch's interests in that legislative body, after PPD gubernatorial candidate Aníbal Acevedo Vilá narrowly beat former Governor Pedro Rosselló after a hotly contested post-election court challenge.

In addition, he became the fourth senator to be elected Floor Leader for 12 years, joining Ruben Berrios of the Puerto Rican Independence Party (PIP).

On November 6, 2012 he was elected to the Senate of Puerto Rico, representing again the District of Humacao, along with his running mate, Jorge Suárez Cáceres.

His cousin Juan Dalmau, is one of the leaders of the Puerto Rican Independence Party (PIP) and is elected in 2016 as senator at-large.

Another relative, Daly Dalmau, was married to former mayor of Carolina, José Aponte de la Torre.