I know that willow and apple branches can be used fresh (according to the House Rabbit Society) and that a few other tree branches can be used as chew stick for rabbits, but they have to be dried for at least a month. I assume that one would just cut the branches and place them in a location where they would dry easily (not in a humid atmosphere), but I don't know if there are any specifics for this.

It's very possible that someone at the SD HRS would give you the instructions on making the wreath, especially if you patronize their store on a regular basis.

not likely that you'll be able to dry out anything in san diego humidity...
here in phoenix i i could leave an apple outside and it would be a hard little golfball the next day

If you're going to make something with it like a ball or a wreath make sure to do it before you dry out the branches!

I would just be careful. If there are pesticides sprayed near the tree I would soak the branches in a Vinegar/Water bath to get them off the branches before drying them out.