Covered California, the state's version of the federal program also dubbed Obamacare, currently has about 1.5 million Californians enrolled.
Executive director Peter Lee is hoping another 400,000 will sign up for 2017.
Lee said at this point we cannot predict how the Trump administration will change the federal program.
"While health care policy doesn't change overnight, your health care can," Lee said. "Overnight you can get cancer. Overnight you can get in a car accident. Going without insurance - you're rolling the dice. That's a gamble we want people to not take."
The Covered California website explains who is eligible and what financial assistance is available to help pay for coverage.
People can enroll online or use the website to find a clinic or hospital to sign up in person. To enroll, you'll need proof of address, proof of income and proof of citizenship or immigration status.
The deadline to sign up is Dec. 15 for coverage that begins Jan. 1, 2017. Those who miss that deadline can sign up by the end of January for coverage that starts Feb. 1.
Since the Affordable Care Act became law, in fact, California has signed up more people than any other state.
So we will likely see the most uninsured, should Trump repeal it.
That has many people who depend on Obamacare on edge.
Spike Dolomite Ward of Tarzana, 54, is fearful of losing access to life-saving treatment.
"I'm worried. I'm really worried," she said.
Ward is a breast cancer survivor and one of 130 million Americans with a pre-existing health condition.
She says even though Trump said he would keep that provision of the Affordable Care Act, any change to the health law will affect her.
"Insurance companies will be in control," Ward said. "They'll charge whatever they want. People with pre-existing conditions are not going to be able to afford it."
Nancy Gomez, with the health consumer advocacy group Health Access, said for many people, Obamacare is a life-or-death issue.
She added if you take away the threat of tax penalties or the promise of subsidies, insurance companies won't be able to afford carrying people who need high-cost health care.
"If you keep the protection for folks with pre-existing conditions then the insurance industry is going to demand that everybody buy into coverage, both healthy people and sick people, because otherwise their model doesn't work," Gomez said.
About 4.6 million Californians bought their insurance through Covered California or were allowed to join Medi-Cal. Experts fear if any part of the ACA is repealed, California could lose $20 billion in funding.
"If there is no mandate and people don't have to purchase insurance, they won't," Gomez said.
Ward was without insurance when she was diagnosed in 2011 before Covered California was created.
But she says President Barack Obama's provision for pre-existing conditions allowed her to have coverage.
"President Obama literally saved my life," she said.
She is hoping that Trump will keep people like her in mind.
"It's a crisis situation," she said. "He's messing with our lives. Literally, messing with our lives."