Opening day for the 2012 Downtown Farmers Market will be May 5, the Downtown Community Alliance announced. The market, which began in 1976 with just 15 vendors, now includes more than 200 vendors on nine city blocks. The weekly event, held each Saturday morning in the historic Court District, this year will extend through Oct. 27. Kelly Foss, Downtown Farmers’ Market director, said the unusually warm spring should mean produce such as fresh strawberries and sweet corn several weeks ahead of the typical growing season this year. Last year’s opening day on Court Avenue attracted a record crowd of nearly 40,000 people.