An issue you might run into with long sleeves in Miami is due to the humidity, not just the summer temperatures.
I tried something like these for a while.
http://www.ebay.com/itm/SARX-Sublime...QAAOSwDuJWxgDP
A good fairly skin-tight but not strangle-tight, "wicking", sunblocking long sleeve is freakin' awesome out in the dry SouthWest.
Unfortunately, the same is not nearly as comfortable
for me here in Southeastern Louisiana from early June through mid-September.
It just gets wet and stays that way unless there's a 14-16mph wind over an above my own speed. Granted, the sunblock benefit is still there, but imagine feeling clammy in 90+F heat and 85% humidity for hours on end due to the sweat not evaporating. Not really fun. (Oh and the sweat stains/deposits at the end of each ride remind me of the Bonneville Salt Flats. Heh.)
My solution, as a recumbent rider, is to wear a non-cycle-specific loose-fitting long-sleeve sunblock
shirt - not too loose so as not to flap, but definitely not a close-fitting, "wicking" shirt.
Just for "completeness", here are a couple links to shirts you might consider:
http://www.amazon.com/Coolibar-Mens-...9Q55V1ZPPJPEZ0
http://www.amazon.com/Coolibar-UPF-M...YPMZ5ZS05FEVVA
Consider the difference/your needs... the 2nd has buttoned neck opening, the first doesn't. Airflow/temperature control is significantly different to me... I went with the 2nd. (Remember, I ride a recumbent...on a DF, I might make a different choice.)
YMMV.
Added: I have also ridden in one of these and felt great - but probably NOT a DF'ers choice of shirt.
http://www.amazon.com/Coolibar-UPF-M...DWDTRXJN60D3C1