At UC Davis.
You can watch it live online at the university's web site; watch it live online on KCRA-Sacramento, or listen live on KQED or on Capital Public Radio.
According to UC Davis, La Opinion will also be streaming it with Spanish-language translation.
KQED's Sacramento bureau chief John Myers will be all over this on his Capital Notes blog. He'll also be on Forum tomorrow discussing the debate, along with the Chronicle's Carla Marinucci.