Omar, welcome to the forum! I regret to dampen your enthusiasm, but Bougainvillea are too happy to keep in hanging baskets in So. Cal. They want to be shrubs...the bigger, the better. There is no way to keep them happy in baskets in the long term. Fast drainage is important as they aren't water hogs, but keeping them confined in small pots will require frequent watering. They really don't like their roots disturbed, but up-potting will be necessary. Much easier to plant in the ground, or LARGE containers.
