Starting at 6AM and ending at 2AM you can buy alcohol (on-premises and off-premises) in California. Private retail stores, grocery stores, and convenience stores, all can sell beer, wine, and spirits.
Sales of any type of alcohol are legal at any store that has an off-premises liquor license, including but not limited to convenience stores and grocery stores. Bars may sell closed containers of alcohol for consumption off the premises. Drive-through liquor stores are allowed.
Legal Age for Drinking/Serving Alcohol - You must be 21 to drink or work at a bar in California, but there is no age limit for handling alcohol in retail stores as long as a manager who is 21 or older is supervising. You can work in a restaurant that sells alcohol at age 18