LOS ANGELES (AP) — One of California’s major health care plans is racing to translate materials into Spanish. A small businessman in Burbank is perplexed over what “Obamacare” will mean for him and his workers. Home Depot Inc., Trader Joe’s and other large employers are slashing health benefits for part-time workers and directing them into the nation’s reordered health insurance marketplace.

President Barack Obama’s health care overhaul gets its public unveiling Tuesday when those marketplaces, also called exchanges, open for business, allowing consumers to comparison shop between insurance plans online. The Affordable Care Act will dramatically change the way many Americans will get health insurance and marks the most extensive change to the nation’s health care system since Medicare and Medicaid became law in 1965.

Polls have shown many Americans remain mystified by the law, and Obama last week acknowledged the change had the nation on edge: “The devil you know is always better than the devil you don’t know,” he said.

To Howard Kahn, chief executive of L.A. Care Health Plan, the biggest challenge will be communicating what the law means to the millions of people it will affect.

“By definition, it will be a bit messy on the way,” said Kahn, whose group serves more than 1 million Los Angeles County residents through free or low-cost health insurance programs, including Medi-Cal, the state arm of Medicaid. Last week, staffers were rushing to complete Spanish translations for some coverage materials.

“People are going to be confused,” he said.

California will see about $300 million in federal money for outreach and advertising, some of which is going to a wide array of groups that are trying to promote the law. Yet uncertainty remains. A Kaiser Family Foundation survey of 2,000 uninsured Californians over the summer found 70 percent said they did not have enough information to understand how the law will affect their families.

With a diverse population of about 38 million, the state is being watched as something of a laboratory for “Obamacare.” Its success or failure here could have broad influence nationally.

The state was first to approve establishment of a new exchange, called Covered California. It also is home to 15 percent of the nation’s uninsured, or roughly 7 million people — a number that exceeds the populations of Arizona or Massachusetts.

“This is where it needs to work,” said Anthony Wright, executive director of Health Access California, a consumer group that supports the health care law and has worked closely with the new state agency. “If we can make it here, we can make it work anywhere.”

Beginning in 2014, virtually all Americans will be required to have health insurance or pay an annual penalty to the government. For residents who have health coverage through an employer, not much is expected to happen on Oct. 1, when enrollment begins. Actual coverage through insurance purchased on the exchanges will start Jan. 1.

Among those without insurance, an estimated 5.3 million Californians will be eligible for coverage through the state-run exchange, officials estimate.

The launch takes place against a backdrop of continuing political unrest over the law and what it will mean, and no one can say for sure what will happen in the coming weeks.

One concern is that many of those who come forward at first will be sick people who have been rejected previously for coverage, while healthy, younger people sit on the sidelines, at least initially.

To balance the books, premiums paid by healthy people, who typically need few services, are needed to cover the cost of care for those with medical conditions. Under the law, insurance companies can no longer deny coverage to people who become sick, one of many requirements that also will increase the cost of coverage.

“It’s absolutely true that those who are the sickest will sign up the quickest,” Wright says. But “you want to cover of pool of people that is big and broad, rather than sick and small.”

Not everyone is likely to be pleased with their options under the new law.

For a lower-income person lacking health coverage, “Obamacare” is expected to be a blessing because taxpayers will pick up the individual’s health care costs through an expanded Medicaid program that has been accepted in California. Generous tax credits will greatly reduce the cost of insurance for lower-income people who make too much to qualify for Medicaid.

Yet critics have warned that costs will rise for many who earn too much for the government subsidies. Many middle class and upper-middle consumers who need to buy their own health insurance will be greeted with high monthly premiums and deductibles, in part because insurers now must offer a minimum of level of benefits in their plans.

Sunder Ramani, a property manager in Burbank and an adviser to the National Federation of Independent Business in California, said he is still trying to figure out the law’s impact.

Small companies — those with up to 50 full-time workers — are not required to provide coverage for their workers under the law, although the new state exchange will offer a marketplace for small businesses to shop for coverage.

In his office, 15 workers receive health coverage through the company, but it’s facing a possible double-digit premium increase. He doesn’t know if his workers will find insurance through the new exchange more affordable or if he should start shopping for a new plan for the company. The former Republican Assembly candidate also worries that the changes could strain ties between management and employees.

“These are things that are all unknown,” Ramani said.