I am a little confused... I am renovating my basement that has cinderblock walls and am adding a bathroom with shower. I have 2x4 framing up, but only 1 wall of the bathroom is on an exterior wall. I have drilocked all cinderblock walls and used R-19 insulation, but did not put any sort of plastic against the cinderblock before framing... After Insulating the Non exterior walls with R13, do I need to put up a plastic vapor barrier before I Hang Sheet rock & Backerboard for tiling? And which side should the insulation face? Toward the shower? Thanks

Yes you do need to put up vapor barrier. See the following:
Keeping the Heat In
And
http://www.buildingscience.com/docum..._download/file