The Cuban government has allowed three former political prisoners to leave the island and promised a fourth he can do the same if he can get a visa out of the country, it was learned Monday.

Alfredo Sánchez Echevarría, the 41-year-old son of a former Cuban education minister, his pregnant wife Gladys Chinea, and Carlos Ramón Ibarra, 32, arrived in Caracas, Venezuela late Sunday evening on Air Panama.

A fourth former political prisoner, Manuel Humberto Reyes, 41, is still in Havana trying to get a visa to Mexico. He eventually would join his family in Bay Harbor.

The four constitute the largest group of political prisoners to be released from Cuban jails and allowed to leave the island since 1961, when, almost 1,200 Bay of Pigs veterans were exchanged for food and medicine.

DIPLOMATIC sources in Caracas told a Venezuelan newspaperman the release was "another gesture of good will towards the Venezuelan government" by the Castro regime.

Sánchez's release was facilitated by the wife of former Venezuelan President Romulo Betancourt, an old-time Castro foe. His stepmother is the secretary of Betancourt's wife.

Sánchez was running a cache of weapons in 1961 on the orders of his father, the late Aureliano Sánchez Arango, who then led an anti-Castro organization. He was arrested after an exchange of fire with Cuban security forces and was sentenced to death. He never was shot because of intense diplomatic pressure from México, Venezuela and Brazil. Instead he was sentenced to 30 years in jail, but served 14.

SANCHEZ and his wife, who was arrested two days after him, married in jail. Both were released from jail in March 1975 and since then, they had been trying to leave the island.

"I'm in a new world," Sánchez told the Caracas newsman shortly after his arrival in the Venezuelan capital. "I have led three lives. The first one was before I was sent to jail; the second was led in the Cuban jails; and the third starts now, free, in a nation of complete liberty."

Ibarra was arrested in May 1969 after landing in the northeastern city of Baracoa with a group of exiles trying to organize guerrilla warfare against the Castro regime.

His wife Marta Monday said she was expecting his arrival in Miami "anytime" and has rented new apartment to welcome him. The Venezuelan newsman who interviewed him in Caracas, however, said Ibarra was expecting his wife to join him in Venezuela.

REYES, the only one still in Cuba, called his father in Miami last Thursday to tell him that he had been given permission to leave the island and was trying to get a visa to México.

The former exile went to Cuba two months before the 1961 Bay of Pigs invasion. He was accused by the Cuban government of being a CIA agent infiltrating the island and was sentenced to 30 years.

Dr. Manuel Reyes, his father, refused to say anything more.

"I wish you would not publish anything else about my son," he said. "It might cause problems over there."

The Committee of 100, an exile organization trying to obtain the release of Cuban political prisoners and headed by Jorge Roblejo Lorie, gave U.S. Sen. George A. McGovern (D., S.D.) a list of names considered of top priority for immediate release.

lbarra and Reyes were the first names on the list.