Post Offices in Walnut Creek, California, United States SearchSearch SearchSearch View: Grid 1View: Grid 2View: Grid 3View: Grid 4View: Grid 5View: List Rossmoor Post Office No Reviews Favorite Fax: (925) 930-0445Phone: (925) 947-0195Retail Hours Walnut Creek Post Office No Reviews Favorite Fax: (925) 930-0445Phone: (925) 935-0256Retail Hours Ygnacio Valley Post Office No Reviews Favorite Fax: (925) 930-0445Phone: (925) 287-9267Retail Hours