Iguanas are defiantly not a favorite species down there.
Next time you go try the Jolly Rodger campground on Grassy Key which is on the north end of Marathon.
They have a ramp and a small marina, and a 17’ Key West would be just fine for the reef on decent days.
Or the Long Key state Park on Long Key has ocean front sites, as does the Curry Hammock on Crawl Key just south of Grassy. Full hookups at Jolly Rodger but not at the ocean fronts, and definatly a need for advance booking.
The Dolphin research center is also located on Grassy Key again worth a visit and a chance to swim with the Dolphins.
Halls diving has several locations in the area including one at the marina on Duck Key at MM61.

Another good fishing option would be Buddy La pointe, Fishing Buddy of Grassy Key, a top shelf guide who would be well worth contacting for an inshore charter.
Or you could go the head boat route on the Marathon Lady.
If you want to learn to fish in the Keys, a charter would be the fastest and cheapest way to start.
Any member here heading to the Keys and owning a Humminbird unit can contact me to meet at the I 95 exit at Vero Beach and download all the Keys Hotspots from my chips. Same ones shown on the Florida Sportsman charts.