The whole Silicon Valley advantage is fading. I went there back in 1997 when it was very hard to find technical jobs in my country (Canada) because a lot of those kinds of jobs gravitated to head office cities for large companies, and many Canadian companies were subsidiaries of large American companies. In Silicon Valley, I learned that most startups fail or are acquired within in a year or so. It's like a lottery. Then I headed to London England, found a job fairly easily and lived there for 10 years or so. Not long ago I returned to Canada, Vancouver this time, and found it loaded with startups and other tech businesses that were more established. Another Canadian city that I am familiar with is Waterloo Ontario and it is in a similar condition. I'm told that Toronto is also overflowing with opportunities both startup and more established stuff. If you are going to play the startup lottery, why not do it among folks you know.
And in case you are wondering what this has to do with Miami, I agree with the OP, just stay home and build your business (startup or otherwise) right there. You still have a ticket in the startup lottery if that is the way you want to go, but just like in SV itself, most of those startups don't last very long.
However, unlike SV, if you stay where you are then you have a better chance of building a normal business that grows incrementally by serving profitable customers, reinvesting profits, and taking a longer term view.
Readers of HN should be very aware that there are startups all over the place, and not just in American cities but in most countries of the world. Silicon Valley just isn't as special as it once was because computers and tech and Internet connectivity is now virtually everywhere that there are cities.