I have thought a lot about this, and I do agree that an eco car with lettering all over it screams salesman.
You could mention it while you are talking prices and show that you do everything possible to keep operating costs down to keep your prices as competitive as possible.
It is a double edged sword where I am. You are just as likely to pull up to a Big Oil man rough neck millionaires house, as you are to pull up to an eco freak millionaires house. Both would look at it differently.
I would go with a small truck and call it a compromise.