Twice a day, San Jose insurance agent Ruben Villanueva offers KZSF-AM La Kaliente’s Latino listeners tips about consumer finance and all kinds of insurance. This month, he’s been reminding his Bay Area-wide audience that Californians need to sign up for health coverage by midnight Monday if they want to be insured on Jan. 1. Many low-income Latinos say they’re just scraping by and can’t afford health insurance, while others fear that signing up could alert immigration authorities to the undocumented family members who live with them.