Enroll America's strategy includes going door-to-door in 10 states—Texas, Florida, Georgia, Arizona, North Carolina, New Jersey, Pennsylvania, Ohio, Michigan and Illinois.
Group founder Ron Pollack noted outreach efforts by others including Connecticut's exchange, which has distributed information at rock concerts it sponsored; pharmacy chains such as Walgreens and CVS, which have promoted the exchanges on their websites and in stores; and hospitals, which have been informing patients ''they can get insurance."
Celebrities such as Jennifer Hudson and Amy Poehler, who met with Obama over the summer to support the law, have also gotten into the act, as has pop singer Katy Perry. Perry last month re-tweeted a Twitter message from Obama to her more than 43 million followers that said, "If you're one of millions of young Americans w/out health insurance, you can get affordable coverage starting Oct. 1."
Pollack said the amount of outreach that's been done to date is "not even close" to what it will be after the exchanges open Tuesday and enrollment continues through March.
"Much of the advertising will occur later on," he said.
That will include what has been estimated as a $1 billion ad campaign by insurers, who are relying on enough younger, healthy people enrolling so that their premiums more than cover the benefits paid to people who get ill or who have pre-existing conditions.
(Read more: What's in a name? Lots, when it comes to Obamacare)
"This is not a sprint, this is a marathon," said Pollack. "We've got 182 dates in the enrollment period, and Oct. 1 is no more important than the other 181 days."
They'll need that time. A Kaiser Health Tracking poll released last week found that only 15 percent of the public, and just 12 percent of the uninsured were aware they can begin shopping in October on the exchanges opening in all 50 states and the District of Columbia.
Claudia Deane, who does polling for the Kaiser Family Foundation, said that in another new survey that examined California's young uninsured, "we looked at the folks in the income range that should be eligible for subsidies, and we found that 74 percent either said they weren't eligible or didn't know they would be eligible."