Sounds like you should be fine. I'd almost say you're in the high zone 9, as if there was a "zone 9c", you would be in it!
I know what you mean about the heat/cold differences. Last time I was up there last year, I was staying in Benicia and went on a wine tour. Then I went to visit some relatives and friends through Walnut Creek and San Ramon, and the temperature difference was about 25 degrees between Benicia and San Ramon. We dressed in long pants and sweaters at the resort in Benicia, and had to change to shorts and t-shirts after Walnut Creek! However the landscape dramatically changes too. After you go through the winding hills of Walnut Creek, it turns brown, from the lush green near the strait.
In your case, you'd be close to my zone's tolerances and growth cycle. The little 'boost' I give to my bananas in about March 20th, is I dump a cu. ft. bag of steer manure on top of each banana stand (or if it's really big, I do 2 or 3). This will help heat the soil, bring them back out of dormancy, and also help break down any decaying material that didn't completely compost over the winter. Also, when it starts breaking down, it releases lots of great nitrogen into the soil. I usually assure a good fruit set by June so that I don't have to worry for many October flags anymore. Nothing is more heartbreaking than a sluggish plant that doesn't do anything till the beginning of fall. It works great, but only if they're in the ground.