A gal I work with has one in her yard here in south Florida, and with the cold snaps we had here the winter of 2010 I'm surprised it lived.

She (by her own account) doesn't take care of it at all and it's thriving on neglect :-) I'm not saying you should neglect yours but her tree may be an indication of just how hardy they are.

I suppose you're keeping yours in a pot and can move it indoors when it gets cold?