Hello, Jennifer!
You can grow them outside if the winter temperatures where they are growing aren't going to go below 2.2º C. Slightly lower temps are possible, but the plants will suffer some damage each winter, and will have to make up for lost time in the spring. They love heat and sun, so southern and western exposures are absolute candy for them. On the other hand, most kinds won't bloom without at least 6 hours of direct sun a day. The purple kinds--varieties of B. glabra--are the most shade and frost tolerant. Bougies are semi-drought tolerant, so if you get a lot of rain where you are, you will probably want to work on giving them extra drainage. Most kinds like a neutral to slightly alkaline soil, but B. glabra prefers a slightly acid soil. They don't normally need much food in the ground, but in containers or confined areas in rockeries, regular applications of rose food help to keep them green and blooming.
There are three main types of Bougainvillea: large, vine-like shrubs; dwarf, vine-like shrubs; and a few are upright-growing shrubs, with leaves close together, and flowers in tight conical clusters at the ends of the branches. In areas with marginal winters, dwarf and upright kinds are easier to tuck into those sunny, frost-free corners. The flowers can be messy when they drop, blowing around freely with the slightest breeze. One way around this is to get "double-flowered" varieties. Their fluffy flower clusters hold onto the "vines", so they don't blow around, though you do need to do a little more pruning, to remove the dead blooms.
Flowers come in shades of yellow, orange, white, pink, salmon, fuchsia, strawberry, scarlet, crimson, and reddish purple--everything except blue or bluish purple. I would give variety recommendations, but Bougies aren't very internationally standardized--the kinds I'm familiar with in the USA are sold under different names in Europe. For extra fun, look for varieties with variegated leaves, edged with creamy yellow, silvery white, or centered with chartreuse.
I hope all this helps!