They just finished construction in that area, the roads are wide and pristine, I drive there daily. It's moderately rough textured but overall smooth.
Here's my idea for the track.
This one has a bit of everything, high speed, low speed, tricky breaking sections long flat out sections. DRS on those bridges is going to be mental
With a total length of 5.1km, lap time will be in the high 1:20's low 1:30's.
This way you have access to Bayside, you close a minimum of a major road and reduce the traffic impact, you're close to a place you can park all the motor homes etc. It minimizes disruption to the port, they would only need to sacrifice 2 terminals, and move operations temporarily.
It leaves plenty of run-off for the braking zones, and we can have a figure 8 layout with left turns in Miami, and right turns over the port. One or two curbs would have to be modified to leave the minimum width needed for a circuit, but I think this is a good layout that is a real challenge for the drivers. The port hairpin would be very interesting, with the layout of the turn requiring some run off, it would be a funnel turn, where the radius increases while the road width decreases.
The high curbs will force drivers to be precise on the run to the stadium even though it's a high speed section. Paint should be used to highlight the dimensions of the curbs for safety reasons. The natural topography of the circuit will limit speeds to reasonable amounts, but not boringly slow either. It also allows the required run off areas.
In this version the pit speed limit would be right after the U-turn so would add an extra challenge, as the pit entry becomes a semi corner where drivers can lose or gain time.
The rich people can watch the race from the cruise ships.