What jadnashua said. R19 may still be code-minimum in some areas of FL but more is still cost effective.
Blown is better than batt as a rule, since it fills in all gaps & voids. In situtions with big temperature differences between attic & conditioned space cellulose retains R-value whereas with fiberglass it's insulation value falls with big temp differences due to induced convection within the fiberglass. With either, a radiant barrier at the roof deck reduces both peak & average air conditioning loads.
If you have ducts, air handlers in the attic they too must be insulated (and radiant barrier affects that too!) If that's the case it's often easiest/best to spray 2-3" of closed cell foam at roof deck as air-barrier/vapor retarder/insulation/hurricane glue for R13-19, sealing all ventilation, and make up the difference in cellulose (up to ~R40 foam+ cellulose) on the attic floor. The interior side of the foam then never reaches the temps where it's radiating a lot of heat, the ducts are inside the pressure boundary of the structure, and the attic temp is now between the roof temp & conditioned space temp. (If you're feeling rich you can make it all closed-cell foam at the roof deck, but it's a pricey proposition.) You could also use 6" of open cell foam in place of 3" of closed cell foam for less money, similar thermal performance, but without the structural & vapor control enhancements.
If blowing cellulose into the attic, it'll perform better if you give it at least 3" over the joist tops to form a thermal-break. R30 is only ~8", and if you have 2x6 joists or bigger the wood makes a large thermal short-circuit through the insulating layer. Wood is also very absorptive of radiated heat, and the joist tops will run hotter than the attic air temp if you don't have a radiant barrier in place. R30 + r.b. is cost effective in FL using even the most conservative assumptions about utility costs, etc., but it's more than just the price of electricity- more insulation will be just plain more comfortable. If you assume energy price inflation (always a difficult factor to prove) or you live in a high electricity price area, R38-R40 can be cost effective as well, and if it covers the joist tops where R30 didn't the performance enhancement will be better-than the simple-math suggests.
Cellulose & fiberglass in walls both deadent sound. In a standard 2x4 framing FG gives you about an STC 38, cellulose dense-packed to 3lbs?ft^3 yields about STC 41 (noticably quieter). At typical loose-blown densities cellulose will still outperform fiberglass, but not by huge margins.
Under no circumstances should an air-conditioned house in FL have interior side vapor retarders. But many can do just fine without any vapor retarders interior or exterior. The issue is vapor drive or air from the exterior finding it's way to a layer inside the cooler building to condense on wood that's below the dew point. If you have stucco or brick siding there is usually a ventilation gap between the siding & structural wall to handle the super-high vapor drives of sun on a rain-wetted siding. In stick-built homes with fiberglass insulation, convection within the fiberglass can transport the high-vapor drive moisture to condense on the cool interior wall-board creating mold conditions- it NEEDS an exterior side vapor retarder. But blown cellulose has only ~10% of the internal convention of fiberglass batts (if dense-packed, less than 2%.) It also wicks condensation away from structural materials and can be used without a vapor retarder in N. FL. But in a flood situation it's miserable- takes forever to dry on it's own and it's usually remove & replace, whereas fiberglass can dry fairly quickly if you open up the walls. (If you live in a flood zone, spray foam insulation would be preferred, as expensive as that is.)