At age eighteen, Guarriello began working as a guard with the United States Marshal Service transporting prisoners to federal penitentiaries from New York City to Lewisburg, Pennsylvania, and Atlanta, Georgia.

His career in the manufacturing industry was short-lived because in January 1944, two months before his twenty-fifth birthday, Guarriello was drafted into the US Military service in the Second World War.

While he was showing medical attention to the wounded soldier, a mortar exploded behind Guarriello piercing him with shrapnel in his left arm and upper back.

On April 26, 1945, while recovering in a hospital in Florence, the Brigadier General awarded Guarriello a Purple Heart for being wounded in the line of duty.

After coming home from the war, Guarriello purchased a house in Long Island, New York and founded a State Farm Insurance Agency franchise.

Guarriello established his Farmers Insurance Company agency franchise there and it continued to be a successful operation until he retired in December 1986, at the age of sixty-seven.

As a resident of West Hollywood and longtime fixture on the Sunset Strip with his friend, the legendary Dean Martin, Guarriello joined the Coalition for Economic Survival (CES), the leading renters' rights organization in 1983.

While striving to be fair and impartial, Guarriello worked hard to protect West Hollywood tenants and the City's strong rent control law.

Guarriello, a gruff but lovable character, was famous for his bust of President Harry S Truman on his modest desk and used the slogan "Give 'em Hell, Sal..." in each of his re-election campaigns.

In 1998, he helped negotiate the transfer of ownership of Santa Monica Boulevard from the State of California, Department of Transportation to the City of West Hollywood.

In 2002, Guarriello, with the assistance of his veteran political consultants Steven Afriat and Neal Zaslavsky, began the recall process against Los Angeles District Attorney Steve Cooley after a gay resident of West Hollywood, Trev Broudy, was nearly beaten to death with a baseball bat by three men, because Cooley considered this crime a robbery rather than a hate crime.

90-year-old Councilmember Guarriello died on the morning of Thursday, April 16, 2009, at Cedars-Sinai Medical Center, surrounded by his friends, family and political supporters.

On May 6, the City Council appointed former National Organization for Women Hollywood Chapter President Lindsey Horvath to complete Guarriello's unexpired term.