changeDateFormat01[s_String] := Block[
  {ss, pp},
  ss = s;
  Do[
    ss = StringReplacePart[ss,
      "'" <> StringTake[ss, {pp[[1]] + 1, pp[[2]] - 1}] <> "'", pp],
   {pp, Reverse@
     StringPosition[ss, RegularExpression["\#\d+\/\d+\/\d+\#"]]}
   ];
  ss
 ]

(* "hello'1/1/2013'hello#donotbefooled#1/1/2013hello'1/1/2013'hello" *)