And is it too cold to plant a few now?

They get huge but I've never seen a large standard. You can use the suggested planting instructions just adjust for your purpose (e.g. if you want a privacy screen, plant them a bit closer together). You might need to manage the crown; these grow naturally in shrub form and if your crown gets too large it might not be structurally sound. Dodonea take well to pruning and even shearing.

You're in Sunset Zone 14 and most of the time Dodonea does fine in your climate. However, if you have a particularly cold winter (such as we did here in Dec 2013), they will freeze, in some cases to the ground. It also is a vigorous self-sower, so much so that I have hundreds of seedlings years after the mother plant died. So I'd use a few for color variation, but I wouldn't rely 100% on this plant for privacy or structure.

You can plant now, always remembering that younger plants are more susceptible to frost damage.

In my experience, these typically grow 10-15ft in height in garden conditions here in SoCal. I've never used them as a screen, more as a single accent as they are quite flammable.

They get pretty big. We have a neighbor that bought a flip that had a front yard hedge of them. They didn't keep them pruned. So now they have a raggedy hedge that is 15-20' tall in the front yard. It looks awful. So keep them pruned up and top them when they get the height you want.