In the spot that has the most sun. Go to your agricultural center for advice. You will probably need a soil test so your garden can grow right. My ag center has lots of pamphlets on lots of subjects. I've learned so much from them. Also check out Solutions For Your Life website and Dave's Garden. I've learned alot from both of them.

What will you grow?

My requirements would be full sun, easy access to an outdoor faucet, and excellent drainage.

Yes, what are you going to grow in your very first garden?

I don't think there's any options there besides full sun, from the pic, unless you go back by the tree line, which would be the perfect kind of 'part-shade,' blocking the most harsh mid-day rays, with well above 6 hours of sun total from the east and west. It would be tricky getting just the right spot that's not too shade, still enough sun.

If plants can get enough sun without baking/drying so harshly, much less tap water can be used, which plants don't usually appreciate because of the chemicals. If you have a rainwater catch system, the tap water part is a moot point, but too much baking is just that, stressful for a lot of plants, often resulting in faux wilt. (You've probably seen pics of tomatoes under gauze netting in really hot places.)

Know that you should check for wilt in the mornings since such baking can cause the faux wilt, which can lead one to incorrectly apply more water, causing a problem where there was none, just a coping mechanism when over-baking in harsh rays and/or high temps.

Generally, orienting long, thin beds with the shorter part being the north/south dimension, plants won't shade each other as much. A 4x4 bed sounds less appealing to me than something like 3x6, where I could access every inch w/o stepping into it or leaning so far. Any plant to the north of another plant will get shaded more, so long and thin can be more productive than square shapes. However, something like lettuce that would love the mid-day shade of a taller plant would go well in such a spot.

Gardening in FL is so different than other places, and even within the state, asking this on the FL forum would probably yield the most applicable info. Between the sandy soil underneath and the beds being raised, you may actually need to attempt to retain moisture in your beds. As a wannabe, a few miles from the border, I lurk the FL forum often. There are often discussion there about building nematode-proof beds, something most gardeners don't have to worry about, AFAIK. I want to be ready if I ever get down there... where the gardening has no off season. The awesome thing about raised beds is that they can be watered in times of drought, and won't flood in times of monsoon. I saw parts of this yard under water for the first time in 7 years, very educational!