Additional Study Information: This is a Phase 1 multicenter study of Decitabine (DEC) and Vorinostat (VOR) followed by the standard chemotherapy drugs (Fludarabine, Cytarabine and G-CSF (FLAG)). The study treatment is considered experimental because it is not approved by the United States (US) Food and Drug Administration (FDA) for treating children with acute myeloid leukemia (AML) which has come back or has not responded to the standard therapy. The purpose of this study is to determine the right dose of DEC when given in combination with VOR before treatment with standard chemotherapy drugs and to find out if DEC and VOR can be given safely together before treatment with standard chemotherapy drugs in children with AML which has come back or has not responded to the standard therapy. Patients will receive decitabine in combination with vorinostat on days 1-5. Patients will receive the chemotherapy drugs which includes Fludarabine, Cytarabine (on days 6 to 10), and G-CSF (FLAG) (on days 5 to 12).