Barbara Karst, shown below, is the best bougainvillea variety for Phoenix because it blooms all year and takes the
heat better than other varieties.
Its blossoms range from purple to violet to pink depending on weather conditions.
Since bougainvilleas are tender right at the
freezing point they are a great indicator plant for growing other tropicals. If the bougainvilleas
in ones yard take very little to no damage during the coldest days of winter then tender plants
such as plumerias and mangoes can most likely be grown outside.
Links to more bougainvillea information
Bougainvillea in Wikipedia