Most Miami itineraries put Little Havana in the evening because it sounds like a nightlife neighbourhood. For twenty-nine days out of thirty, it is not.
SW 8th Street is a one-way commuter road. Between about four and seven it carries traffic out of downtown, the pavements get loud and fume-heavy, and browsing a street you keep having to shout across is not much of an activity. Several of the things worth stopping for — the cigar rooms, the galleries, the fruit stands, the domino tables — keep daytime hours and are simply not there after dark.
The bars and live music venues on the strip are genuinely good and they do run late. But that is a different visit with a different shape: one venue, one long sitting, a rideshare each way. It is not a walk.
The exception is the last Friday of the month. Viernes Culturales closes the street, brings galleries and musicians out, and turns the same blocks into an evening event. If your dates include one, that is the night to come, and the daytime block can be dropped entirely.