Saint Francis Dam Disaster National Memorial Act This bill authorizes the Department of Agriculture (USDA) to establish the Saint Francis Dam Disaster National Memorial at the Dam site in Los Angeles County, California, to honor the victims of the Saint Francis Dam disaster of March 12, 1928. The Memorial shall be managed by the Forest Service. USDA shall submit to Congress, by three years after this bill's enactment, recommendations regarding: the planning, design, construction, and long-term management of the Memorial; the proposed boundaries; a visitor center and educational facilities; and ensuring public access to the Memorial. The bill establishes the Saint Francis Dam Disaster National Monument on specified National Forest System land administered by USDA in Los Angeles County for the purpose of conserving and enhancing the cultural, archaeological, historical, watershed, educational, and recreational resources and values of the Monument. USDA shall develop a management plan for the Monument by four years after this bill's enactment. USDA shall manage the Monument: (1) in a manner that conserves and enhances its cultural and historic resources, and (2) in accordance with the Forest and Rangeland Renewable Resources Planning Act of 1974. The bill limits the use of motorized vehicles but permits grazing within the Monument.