If you put turbines anywhere the drag will definitely increase as a result, and the amount of energy generated will certainly be much lower than what's lost due to the increase in drag, since no system (and certainly not a mini wind turbine) has 100% efficiency.
I don't want to be belittling but please think of what you're proposing... Free energy anyone?
I don't see this as a "free energy" scheme or anything like a perpetual motion machine. In the case of a car moving through the air, you have conceded losses to wind resistance. Think about that, you have energy that you are going to lose to drag and you know it. The goal of the wind turbine is not to create energy, it is to lose less energy, huge difference and the reason why something like this is not against the laws of physics.
It does no matter that a wind turbine is not 100% efficient either, because you are working to reduce the loss of energy, not make energy.
Imagine the Jeep people are talking about, presumably has electric fans for the radiator. If those were acting as turbines during highway cruising, the drag would not increase and they would make energy...albeit not very much. The reason it is not free energy is because it is a trick to allow the jeep to waste less energy pushing air, and that is all.