You could definitely use the help at RB so I would say go for it! Bush is a good short term value and a spot start but nothing long term there in my eyes! RG3 has a lot of long term value but MJD would definitely boost your RB.
QB: Jake Locker, Ryan Fitzpatrick
RB: Jamaal Charles, Adrian Peterson, Trent Richardson, Peyton Hillis
WR: Dwayne Bowe, Vincent Jackson, Jordy Nelson, Marques Colston, Kendall Wright, Michael Floyd, Alshon Jeffery
TE: Vernon Davis, Heath Miller