Cuba and Venezuela angrily denounced the release. In Havana, hundreds of students staged a protest outside the U.S. diplomatic mission, chanting "Down with Imperialism. We demand justice. Long live Fidel."
Posada Carriles, 79, posted bail totalling $350,000 (175,000 pounds) to get out of a federal prison in New Mexico.
He travelled to Florida on a private jet and was greeted by his family at Miami International Airport, a U.S. Marshals Service spokeswoman said. He was taken by car to his wife's suburban Miami home where he will stay until his May 11 trial in El Paso.
Posada Carriles has been in custody since May 2005 after he entered the U.S. illegally to seek asylum. In January, he was indicted on seven immigration fraud charges accusing of lying to immigration authorities.
His release on bail was granted by U.S. Judge Kathleen Cardone and ended a long fight by the U.S. government to keep him behind bars.
His lawyers had expected him to be taken immediately back into custody on an immigration detention order, but that did not happen.
The government said he had been given a list of conditions for his release, but it did not explain why the former CIA operative accused in various plots against Cuban leader Fidel Castro was allowed to go free.
Department of Justice spokesman Dean Boyd said, "We expect him to appear in court on May 11 for his criminal proceeding as ordered."
EXTRADITION DEMAND
In Venezuela, President Hugo Chavez, a vocal U.S. critic, told a political event in Caracas, "We demand they extradite that terrorist and assassin to Venezuela instead of continuing to protect him in the way they are protecting him."
"They say they fight terrorism but that mask of theirs slips all the time," he said.
Dagoberto Rodriguez, chief of the Cuban Interests Section in Washington, said, "Cuba emphatically condemns this decision and holds the U.S. government entirely responsible for Posada Carriles being free in Miami."
Posada Carriles is wanted in the two leftist countries for trial on charges he masterminded a Cubana airliner bombing that killed 73 people. He is a naturalised Venezuelan citizen and lived there at the time of the bombing.
Cuba says U.S. authorities are protecting Posada Carriles by prosecuting him on immigration charges and not terrorism.
"Why don't they try him for terrorism?" the president of Cuba's National Assembly, Ricardo Alarcon, told reporters. "Because a trial against Posada Carriles would be a trial against Bush Jr. and above all against his father, who headed the CIA when Posada Carriles committed his worst crimes," he said, referring to U.S. President George W. Bush and former President George H.W. Bush.
While Cuba and Venezuela view Posada Carriles as a terrorist, many in the politically powerful Cuban American community support his anti-Castro acts.
Castro, the ailing Cuban leader who has not appeared in public since emergency surgery in July, accused the American government last week of harbouring his nemesis.
"Not a single word has been said about his countless victims, his bomb attacks on tourist facilities in recent years or dozens of his plots financed by the U.S. government to eliminate me physically," Castro wrote.
Posada Carriles was jailed in Panama for a plot to assassinate Castro during an Ibero-American summit in 2000, but was pardoned by outgoing President Mireya Moscoso in 2004.
Cuba also accuses him of plotting a wave of bomb blasts in Havana hotels in 1997 that killed an Italian tourist.
Under terms of the court order that freed him, Posada Carriles will be under house arrest in Miami and will have to wear an electronic monitoring device.
(Additional reporting by Jim Vicini and Adriana Garcia in Washington, Anthony Boadle in Havana, Jim Loney in Miami and Ana Isabel Martinez in Caracas)
Reuters (IDS)