 This phase I trial studies the side effects and best dose of iodine I 131monoclonal antibody BC8 when given together with fludarabine phosphate, cyclophosphamide, total-body irradiation, and donor bone marrow transplant, and to see how well they work in treating patients with acute myeloid leukemia or acute lymphoblastic leukemia that has spread to nearby or other places in the body advanced, or high-risk myelodysplastic syndrome. Giving chemotherapy drugs, such as fludarabine phosphate and cyclophosphamide, and total-body irradiation before a donor bone marrow transplant helps stop the growth of cancer or abnormal cells and helps stop the patients immune system from rejecting the donors stem cells. Also, radiolabeled monoclonal antibodies, such as iodine I 131 monoclonal antibody BC8, can find cancer cells and carry cancer-killing substances to them without harming normal cells. When the healthy stem cells from a donor are infused into the patient they may help the patients bone marrow make stem cells, red blood cells, white blood cells, and platelets. Sometimes the transplanted cells from a donor can make an immune response against the bodys normal cells. Giving cyclophosphamide together with mycophenolate mofetil and tacrolimus after the transplant may stop this from happening. Giving a radiolabeled monoclonal antibody together with donor stem cell transplant, fludarabine phosphate, cyclophosphamide, mycophenolate mofetil, and tacrolimus may be an effective treatment for advanced acute myeloid leukemia, acute lymphoblastic leukemia, or myelodysplastic syndromes. 