A freeze will kill it. A frost probably will as well. I kept one in a large pot fpr bout five years, moving it indoors in the winter.

I don't it will survive in the ground in your area. Maybe someone in your area will see your question and respond to it.
Kay

Hi Cara,
I am also gardening in zone 9, although I'm on the east coast. I have several bougainvillas in my garden and they have been very robust plants to say the least. We may have a slightly warmer winter than you but the few freezes that we do have only only burn back to folage a bit. I cover the root and trunk area if a freeze is forcast and the plant bounces back in the spring. I have mine planted against the west side of my house and on a south facing fence. So it may not be as happy in an open, unprotected area.
Give this plant plenty of room and good support, it can get HUGE and quite heavy. The thorns are wicked so it could make a good security fence, but it can be an adventure to trim back. Think stout pressure treated wood and rebar instead of fencing wire and posts. I have one of mine on a welded rebar arbor and the other is growing on a stout wood pergoda that my DH built just for it. Like you, I had no idea what this plant would do when I planted it and it took over one whole corner of my yard. I have a low tolerance for unruly plants but the flowers are so beautiful that I decided to make allowances and spend some money on heavy duty supports.
Bougainvillea takes pruning very well. I have cut mine back severly several times and it always bounces back bigger than ever. I have seen them trained into a shrub, small tree and even hanging baskets. It would just take a bit of diligence to keep it shaped as you would want it. In my experence, when bougainvillea is planted where its happy, it's a beautiful plant with plans to take over the world. Keep your pruning shears sharp.
Happy gardening, Cindy

Thanks for all the information!