Residents are protesting plans to build a community plaza in an unincorporated area north of Downtown Sonoma. A developer wants to use a public-private partnership to build the plaza in the Springs neighborhood, just north of the historic Boyes Hot Springs Post Office on Highway 12. The plan, first proposed last month, saw quick push back. Residents are concerned about traffic, the use of public funding, and a possible underground parking garage. They’re also concerned about the developer, Ken Mattson. He and his wife have bought more than 60 properties in the Sonoma Valley in the past seven years. But, many of those properties are still vacant, or in a state of semi-repair.