Since 1991, San Miguel had been competing in numerous tournaments across Spain and Europe, and had won several medals, including her first title at the 1998 European Judo Championships in Oviedo. She was selected to compete for Spain at the 2000 Summer Olympics in Sydney, where she was defeated by South Korea's Lee So-yeon in the repechage bout of the women's half-heavyweight category (78 kg). At the 2003 World Judo Championships in Osaka, Japan, she made her international breakthrough by winning the bronze medal in the 78 kg class.