GRASS VALLEY, Calif. — Here in the rugged foothills of California’s Sierra Nevada, the streets aren’t littered with needles and dealers aren’t hustling drugs on the corner. But meth is almost as easy to come by as a hazy IPA or locally grown weed. Quinn Coburn knows the lifestyle well. He has used meth most of his adult life, and has done five stints in jail for dealing marijuana, methamphetamine, and heroin. Now 56, Coburn wants to get sober for good, and he says an experimental program through Medi-Cal, California’s Medicaid program, which covers low-income people, is helping. As part of an …