Sex links just means they've taken 2 varieties or breeds and crossed them to produce chicks that can be easily sexed at hatch (ie; the cockerals have different markings/coloring than the pullets do). Blacks are a cross between a Rhode Island Red or New Hampshire rooster and a Barred Rock hen. They are not all black but are mostly dark colored when grown. Red & golden sex links are a cross of different Road Island and/or New Hampshire varieties.
They are all great layers and are well suited to the heat of your area. Buff Orpingtons, on the other hand, are not well suited for hot areas. They do very well in colder areas becaue they have a thick layer of down and feathers. They will also lay well through much of the winter because of this. As I'm sure you know, here in Reno we unfortunately get both heat in summer and very cold temps in winter. So I do have Buff Orps but I have to be careful to give them ways to cool off when it gets over 80 like Peep_Show mentioned (sometimes over 100 here too but not quite as hot as you get down there and not as often).
The pure bred Araucana is extremely rare in the U.S. so when a feed store or a hatchery says they have Araucanas or Ameraucanas (actually two different breeds, but both lay a blue egg or mostly blue with a slightly greenish cast) they really mean they are EEs. An EE or easter egger is just a mixed bird with ameraucana or araucana (usually ameraucana since araucanas are so very rare) in their mix. They can lay a green, brown, blue, white or even a pinkish colored egg. Since most feed store owners don't know this much about the history of the breeds they sell I don't bother correcting them about the true breed of ameraucanas, araucanas and EEs. It is really the hatcheries' fault for misrepresenting their birds not the feed store's fault. They are just repeating what the hatcheries have told them.
I do have EEs and I am getting some purebred ameraucanas in a couple of days (from a breeder). I have Rhode Island reds and Golden sexlinks as well as Marans, Welsumers and Blue Orp crosses. I had some Plymouth Barred Rocks but I lost them recently. This mix gives me a huge variety of color in my egg cartons which is what I want but since you want heat hardy birds I would stay with the sexlinks, Rhode Island Reds and Barred Rocks. The EEs have a rose comb and don't throw off the heat as easily as a large comb will. The Rhode Island Reds and Sexlinks are the best layers of all these breeds.
Well now you have a lot more info on the breeds you mentioned, good luck with your new flock whatever you decide.
