BY ELAINE DE VALLE

  Calling his four-day visit to the heart of Cuban America a success, Oswaldo Payá Sardiñas left Miami on Tuesday for Mexico City, where he hopes to garner the support of President Vicente Fox for Cuban dissidents.

  Before boarding his flight at Miami International Airport, Payá said he would take a piece of Miami home to Havana with him.

  He reiterated the message of unity between South Florida's Cubans and Cubans on the island that ran like a thread through his visit.

  ``We are one single people, those inside and those outside.''

  He came to Miami to nurture solidarity and enlist support for the Varela Project, which seeks a referendum calling for freedom of speech and association, amnesty for political prisoners and free and open elections in Cuba.

  ''I have to express my gratitude for the warm way I was received,'' he said, calling his visit an example of what an encounter between Cubans on the island and Cubans in exile can be.

  Responding to critics who oppose his initiative because it works within the system of Fidel Castro's government, the noted Cuban dissident said he welcomed dissent from that faction of Miami's exile community because it shows that Cubans are diverse in thought.

  He also said he felt the Miami community was his community. ''Their errors and their defects are ours, too,'' Payá said.