Subprime lenders have set their sights on a growing but reportedly underserved segment of the mortgage market, Hispanic borrowers. A case in point is Option One Mortgage, which last week launched a partnership with San-Diego based Prado Mortgage Corp., a mortgage banker specializing in the Hispanic market. Through the partnership, Prado, which gets about two-thirds of its $25 million monthly volume from the subprime market, will offer Option One’s product suite borrowers through its broker