Looking at the photographs that's definitely C. fistula. From personal experience in Australia I can confirm that C. fistula will withstand very hot climates, if it gets some supplementary water during summer. It does not require enormous amounts of water - I'd say on par with citrus trees.
It is very sensitive to frost however and needs a sheltered spot. I have seen it growing well in Port Augusta, an inland town in South Australia where summer temperatures can stay above 40C for 10 or more days, while winter temperatures could drop below 2C. Initially our neighbour had a single tree that she grew from seed collected in the sub-tropics but my mother grew dozens of others from seed, selling them at school fetes etc and soon there were many growing in the town. The spring flowering was truly spectacular I remember standing under that first tree as a child and the whole world seemed to turn bright daffodil yellow as the sun filtered through the blooms. The leaves are rather attractive too retaining a lovely fresh green color. The trees in Port Augusta however seldom grew more than 3-4 metres high while those I have seen in the sub-tropics around Cairns and Darwin in Australia are more than 10m high. Cheers Anita