Can't say much for Miami but in the Florida Keys, some ideas:
*Snorkel John Pennekamp Coral Reef State park.....http://www.pennekamppark.com/
*Visit the Dolphin Research Center on Grassy Key, about halfway to Key West.
*Drink. Early and often.
*Hop a fish charter out of the many marinas up and down the Keys. Even though this is a fishing mecca year round, many of the top trophy fish run in the summer.
*In Marathon,at the airport, you can ride in a genuine Czech built Albatross jet trainer. Bring coin though, pricey.
*Bahia Honda State park..on the far end of the Seven Mile Bridge from Marathon. Best beaches in the Keys.
IN KEY WEST
*Duval Street. All I need to say...you'll figure out something to do when you get there. You did mention you're straight, so most of the fun for you lies from about Fleming Street north.
*Take in a sunset aboard the schooner Wolf, the flagship of the Key West schooner fleet...http://www.schoonerwolf.com/
* Gotta make the obligatory trip to Ernest Hemingway's old watering hole....http://www.sloppyjoes.com
....also, visit his actual home, now a museum. http://www.hemingwayhome.com
*Frisky? Shed it all on the roof of the Whistle bar at the daring Garden of Eden (don't worry it's straight! at least theoretically.)http://www.thebullandwhistle.com/eden.htm
*Visit Sunset festivities on Mallory Square. Just follow the crowds, it's a Key West rite of passage.
*Have I mentioned drinking?
*If you're bar hopping, don't forget two rustic off-Duval watering holes actually still frequented by the island's slightly demented locals http://www.greenparrot..com
*Check out Fred Cabanas biplane and stuntplane rides at KW International...If I remember correctly, he's got a 1940 Stearman and a hot rod Pitts special. I'm told a sunset ride aboard one of them is amazing.
Enjoy! Too bad you weren't there a little earlier....I'll be there with some buds Aug 8 thru 11th. That's the plan
, anyway. Knowing Key West, I very well may still
be there when you arrive.