great question.....

Here in Phoenix, Alpinia zerumbet the shell ginger and A. zerumbet Variegata does not die back in winter...unless it hit by a hard freeze...which never really happenes here...so it should not die back in Miami....

You should be able to grow most gingers where you are. I have a similar climate here in Queensland and none of my gingers go dormant. Most Costus should do well along with the many varieties of Zingiber spectabile (Zingiber zerumbet goes dormant), Etlingera Torch Gingers, Alpinia, Hedychium, Tapeinochilos. None of these plants will go dormant and die down in winter.

Andrew.

i have a costus, shell, hedychium and cardmom ginger that do not die back here in 9b.