For more than two decades, small-scale farmers and community gardeners have grown fresh fruits and vegetables, native plants, flowers and other produce at the Tijuana River Valley Community Garden, a 20-acre complex of publicly owned farmland adjacent to the Tijuana River. … All of that came to a halt last week when representatives from the Resource Conservation District of Greater San Diego County, which manages the garden, issued mass eviction notices to all 217 community gardeners and farmers. One reason for the sudden eviction, the district’s executive director said, was a series of pollution warning signs erected six weeks ago at several locations throughout the river valley, including at the garden itself.