We’re going to Miami for a full 3 days at the end of March. Can anyone recommend a day trip to one of the Florida Keys.
The most we’d want drive is 2 hours. Which Key would have the most to offer? Maybe we’d take a short cruise and check out a town or two.
Thanks.
First of all, how long it takes to drive to one of the Keys depends upon where in Greater Miami you are starting from. It is also very traffic dependent, since a long stretch is one lane each direction.
Key Largo is filled with stuff to do. It captures the essence of the Keys while staying fairly close to Miami (it’s anywhere from one to one-and-a-half hours away).
Islamorada is about half-way down the Keys, IIRC. There is plenty to see there, and some good restaurants, if my shaky memory serves me correctly.
Don’t try to go all the way to Key West in one day and back; it’s not very feasible, unless you like long drives that start early and end late.
That key that Schwarzenegger nuked is probably still radioactive, so I’d be cautious. 
In 2 hours, very little is possible except maybe Key Largo as someone already pointed out. You can visit John Pennekemp State park and go on a glass bottom boat trip to the coral reefs (not for the sea sick kind). You can also go on snorkeling trips from key largo or just do snorkeling on the beach at John Pennekemp.
[Moderating]
This is better suited for IMHO. Moving.
If you are in the Keys at the end of March we are having a Blue Angels air show on March 30 and 31st. You will have to get near Key West to see it. The main airfield at Boca Chica Key will be open to the public.
You could just head to Key Biscayne. It’s pretty damn close, and has a nice park on it, on the beach.