In California, more than 8 million people lack health insurance. According to a Bee analysis of U.S. census data, that number includes one in six Sacramento County residents.

"Our members expect that we will have a shortage of primary care physicians," Sandberg said.

A key focus of the legislation is to promote early visits to primary care doctors to save the system from expensive surgeries, complications from chronic diseases and other advanced illnesses. But medical schools have been producing fewer primary care physicians, with many students opting for more lucrative specialties that will allow them to pay back school loans.

Primary care physicians have long complained about meager reimbursements from government health programs, such as Medicare and Medicaid, known in California as Medi-Cal. Despite an expected boost in funding for Medicaid included in the federal legislation, it won't be enough to entice doctors to accept more of those patients, says the California Medical Association.

Still, some experts say fears of a big shock to the health care delivery system are likely overblown.

It's not as if the uninsured would all come rushing at once for medical coverage, said Marian Mulkey, a senior program officer with the nonpartisan California HealthCare Foundation.

While some parts of the federal legislation, once signed by the president, could be implemented as soon as this year, most of the major provisions won't come on line for another three years. "There won't really be a sea change until 2014," Mulkey said.

"It's not as if all 32 million will get insured in the first possible year," she said.

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Many of the newly insured could get services at community clinics like The Effort. As much as $11 billion in federal funds could be distributed to federally qualified health centers to help them expand services.

As more people get insurance, hospitals expect an easing of emergency room visits by the uninsured. But the problem is unlikely to go away completely, said Scott Seamons, a regional vice president for the Hospital Council of Northern and Central California.

"I know there are a lot of questions about how all this will bear out. But I do believe that hospitals are positioned well," Seamons said.