I have no idea how much money you need, as it depends on your spending habits.

What I DO know is that it is best to bring cash dollars and change them at the "blue" rate in BA. I have several threads about the "blue" rate. At this time, you'd save around 25% versus paying with your CC.

Sunday SHOULD not be an issue for car rentals. Check with whatever firm you are planning to use, be it Hertz or Localiza.

Have a great time in our country.