Flex Fuel for All Americans Act - Amends the Internal Revenue Code to allow a tax credit for the purchase of a new qualified flexible fuel motor vehicle and an additional credit for the purchase of an optimum flexible fuel vehicle. Defines "new qualified flexible fuel motor vehicle" as any motor vehicle which is capable of operating on blends of gasoline, ethanol, methanol, diesel, and biodiesel fuel and "optimum flexible fuel vehicle" as a flexible fuel vehicle certified by the Environmental Protection Agency (EPA) to achieve certain higher levels of fuel efficiency.