Discovery Cruise Line, a Miami-based line that sails to the Bahamas, has signed a letter of intent to sell its cruise operation to Global United Limited, based in the Bahamas. Rafael Ordoñez, owner of Discovery, said Thursday he plans to sell the company's 1,000-passenger ship and other assets. Terms of the deal, which is based on Global United's ability to secure financing, were not disclosed. Discovery operates daily cruises from Broward County's Port Everglades to Freeport on Grand Bahama Island, catering to people traveling between South Florida and the Bahamas for vacation, shopping and visiting relatives. Global United said it has no plans to change Discovery's ''route structure'' and expects to retain its management and staff, according to a statement. Discovery employs about 100 in South Florida.