Historic preservation groups are launching a partnership with city officials to save Miami's Little Havana, the epicenter of the Cuban diaspora.  The National Trust for Historic Preservation added Little Havana to its list of ``national treasures'' Friday, saying it should be protected from developers who are transforming much of Miami's downtown and its surroundings.     The nonprofit says the designation will help organizations, city officials, residents and investors to preserve the area's historic buildings and keep it affordable to working-class dwellers.    The neighborhood's signature street, Calle Ocho, features cigar shops, art galleries and mom-and-pop stores where Cubans and their descendants reminisce about the island.    The historic trust's website says Little Havana faces multiple threats, including development pressure, demolition of historic buildings, displacement of existing residents and zoning changes.

The National Trust for Historic Preservation added Little Havana to its list of ``national treasures'' Friday, saying it should be protected from developers who are transforming much of Miami's downtown and its surroundings. The nonprofit says the designation will help organizations, city officials, residents and investors to preserve the area's historic buildings and keep it affordable to working-class dwellers.    

The neighborhood's signature street, Calle Ocho, features cigar shops, art galleries and mom-and-pop stores where Cubans and their descendants reminisce about the island.  The historic trust's website says Little Havana faces multiple threats, including development pressure, demolition of historic buildings, displacement of existing residents and zoning changes.