I'd put vents atop the window (or high on SOME wall(s), anyhow), for sure.
Reasons being 1) you can never have too much ventilation available, especially when you live somewhere that gets hot; and 2) on cold damp breezy days in the winter you are not going to want to have those windows open and even if you did they won't give you as good ventilation as a high-up vent would.
Of course you can survive without a vent atop the wall, but since it is just about as easy to put one in as not, and it will make your life easier in the future, I'd sure do it.