I can only recall what Steve W, formerly of FL and recently, if not currently, serving in Iraq posted years ago and that is that he cut back, dug, divided if wanted and let them 'rest' for about 6 weeks before replanting in your warm climate. Mulched, amended the sandy soil, and watered like crazy in your high heat. I have no idea when he did the digging. Perhaps you can search for other threads on growing in Florida by him or in general.

Thanks Steve W, for your service, for probably trying to grow dahlias in Baghdad, and possibly succeeding.

Here is a link that might be useful: Link on Growing in FL

Thanks Poochella :)