By RICARDO CASTILLO MLK III at Guerrero Homage Martin Luther King III, the eldest son of U.S. civil rights activist MLK, Jr., was the keynote speaker Sunday, Feb. 14, at the homage paid to the memory of Mexico’s second president, Vicente Guerrero. Guerrero was killed 190 years ago at Cuilápa, Oaxaca. Guerrero, a descendant of African slaves brought to Mexico,