Restaurant workers are typically young. They typically work part time. And they typically can't afford health insurance. Yet the nation's cooks, servers and dishwashers recently found themselves being courted by some of the nation's biggest health insurers. Their trade group, the National Restaurant Association, was able to line up a smorgasbord of individual and small-group plans from UnitedHealth, some priced 15 to 20 percent cheaper than the open market. The potential prize for UnitedHealth: access to 13 million restaurant workers, between 4 million and 6 million of whom currently have no insurance.