More than 400,000 Californians have signed up for a private health care plan through the state's new online insurance exchange that opened for business Oct. 1. An additional 460,000 are now eligible for Medi-Cal, the state's health program for the poor that was expanded under the Affordable Care Act, commonly known as Obamacare. Despite all the new potential patients, hospitals and medical clinics from San Jose to Oakland to Walnut Creek reported that they haven't yet been overwhelmed with previously uninsured people seeking care.