He joined The Electric Company with Denise Nickerson (who was in only season two), and they replaced Irene Cara (who was in only season one and recently departed in 1972) in season two, playing, most notably, Doctor Doolots. He was in seasons two through six of this show. He was good friends with fellow Electric Company star Rita Moreno. His most notable movie role was as Ramon in the 1979 comedy Hot Stuff, in which he starred alongside Jerry Reed, Dom Deluise, and Suzanne Pleshette.

Avalos appeared on the Barney Miller show. He was in the episode "Chase" in 1977 and also the episode "Bones" in 1982.

Ávalos also starred as Jesse Rodriguez on the short-lived situation comedy Condo with McLean Stevenson, and as Dr. Tomas Esquivel on the short-lived situation comedy E/R with Elliott Gould and Mary McDonnell. He played Dr. Sanchez on Highcliffe Manor on NBC in 1979 and Crecencio Salos in Ned Blessing: The True Story of My Life on CBS in 1993. Additionally, he starred as Stavi in the comedy The Ringer with Johnny Knoxville.

In 2000, he founded the Americas Theatre Arts Foundation in Los Angeles to support Latin American-inspired dramatic productions.

Avalos died on January 22, 2014, of heart failure, after a heart attack. He was buried at Forest Lawn Memorial Park (Hollywood Hills) in Los Angeles at Burbank.