I have tried to grow this tree in Southern California. It doesn't do well here. Still too cold. I still have one big one left after about 15 years, about 3 inch trunk and 5 feet tall, but it would die back a little every winter. It is impossible to bonsai. The leaves are too big and can not be reduced. Unless you want an imperial size bonsai. But I would not bother with this tree unless you are in a truly tropical climate with no chance of freeze.
By the way, that picture is fake. The leaves are about a foot long and compound. The flowers are really big too, 4-5 inches across. I love this tree, since it is almost the national flower of South Vietnam. They used to grow these trees along the streets there. It is spectacular when in bloom. They are fantastic in Hawaii too. Maybe you should try it. You never know, you might be the first to successfully bonsai this beauty.
Good luck to you.
Si