There are avocados that are hardy down to about 15 degrees. That said, those temps are for mature trees.
I grew a Mexicola Grande improved in California Zone 8 but for the first 5 or 6 years of its life, the trunk was wrapped in Christmas tree lights (the old fashioned ones that give off heat) and the top had a shop 'trouble' light hanging in it.
If your winter temps never drop below 15 or 20 degrees, you could. Also, the earliest avocado trees produce fruit is at 3 or 4 years old. Mine didn't set fruit until it was almost 9 years old.
