Eve, your poinsettia should do fine planted outdoors in a sunny spot. They're native to Mexico so you're not too far away from where they grow naturally. They can make very large shrubs, and if it happens that the temperature falls too far, they might lose all their leaves for a time, but will re-grow them. A good mulch is a help to keep the roots warm and moist if cold weather threatens.
If you can manage to plant it somewhere that the house lights, outdoor lights and street lights won't hit it, it will also do its own thing and turn red on cue in the fall, once the days get to the right length.