Since no one from Zone 10 has answered, I'll give it a shot. I find C. erythrophyllus (the dark leaved form) to be somewhat tolerant of cool weather - more so than some others like C. malortieanus which absolutely melts away. If zone 10A means no prolonged cold below 40 degrees, you should be fine with it. Might get a little leaf damage but not much.

Cultural needs - light or filtered shade, well drained soil kept regularly moist.

Thanks for your response. I also bought costus malortieanus! I will have to work at finding the best microclimates soon.