I am from Miami, work in finance and been following the mkts since 2005 or so. This story has been going on since I can remember. It is BS. First of all, Singapore became hot because of the extremely favorable taxation for corps and funds, and because it was for many a place to hide money.
Other than the no state tax thing, Miami does not have any of that. All I see in Miami is a bunch of big firms with their financial advisers flirting with South American clients, that's it. Hedge Funds and prop trading firms come and go and the talent is simply not here. Spoke to at least two prop trading firms that were here (First NY and Trillium) and in both cases they were either shutting down or downsizing.
Plenty of rich people in Miami, but most of them spend only a few months per year here to have fun, then they go back north were they really make their money and usually use their local broker there. The rich money that stays here is old money, people retiring...nothing exciting in other words.
Btw the firms that deal with Latin clients (UBS, Credit Suisse, HSBC and Merrill) are under so much scrutiny all the times that it is a pain in the ass to transact business that way. Already Brazil has gone after a few clients and Merrill brokers for helping Brazilians hide money here. It is only going to get worse with time.