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 2004 Summer Olympics in Athens, San Miguel lost the first preliminary match to Great Britain's Rachel Wildin, who scored an automatic ippon in the half-heavyweight event.

She reached the semi-final round of the event by beating Vera Moskalyuk of Russia, Brazil's Edinanci Silva, and Lucia Morico of Italy in the previous preliminary matches.

[3] With her opponent advancing directly into the finals, San Miguel proceeded to the bronze medal match, where she lost to France's Stéphanie Possamaï by a high-scoring waza-ari, finishing only in fifth place.

[4][5] At the 2009 European Judo Championships in Tbilisi, Georgia, San Miguel won a gold medal for the half-heavyweight division since her first title in eleven years, defeating Ukraine's Maryna Pryshchepa in the finals.