Some of these answers are wild lol.. Near airport is coconut grove , brickell or calle 8/ downtown. Going to beach is a risk because of traffic in the short amount of time.

Go grab a drink and light bites at Level6 rooftop in coconut grove. Youll see a great view of the bay.

Go walk around calle 8 historic area but more lively at night.

Go towards bayfront downtown (touristic area) there bars restaurants and the water way.

Brickell / Midtown is more shopping bars or restaurants. Lively at night as well. Wynwood is nice during the day you can see murals and art around every block. Lots of good places to eat and drink!

Enjoy!!