I've been searching for good coffee in Miami for a few years now. There are several places to try, starting with Cafe Paul on Lincoln Road in South Beach and the predictable Starbucks. Espresso should never be served in a to-go cup, however.
There is also great Cuban style coffee everywhere if you like the thick sweet coffee they make.
However, I haven't found a place that makes really great espresso with love and care for each individual cup.