The game is designed that each player is supposed to pick a team to play from each racing circuit/group (Old Folks, Soccer Moms, Redneck and Hippies). So you should have one place playing a team from each of those groups.
All placards are printed front and back but for same group. So if you choose a redneck placard no one should need the back of your placard because they should be choosing from one of the other race groups.
The balance was built so that the various groups would mix well together and provide variety. If you wanted to you could choose to allow people to pick from same group but would have to understand the placard limitation.