Miami International Airport: The sensible cheap transfer is the MIA Mover to the Miami Intermodal Center, then Metrorail’s Orange Line south to Douglas Road (the useful stop for Miracle Mile/downtown) or University (for the University of Miami). Budget roughly 35–50 minutes to Miracle Mile once you add the free Coral Gables Trolley from Douglas Road; rail fare is about $2.25, trolley free. With bags, a rideshare directly to a Coral Gables hotel is often worth it: about 15–30 minutes outside rush hour and roughly $20–35, traffic permitting.
Fort Lauderdale–Hollywood International Airport: Use FLL only if the airfare saving is substantial. A rideshare is the practical choice—roughly 45–75 minutes and often $45–80 depending on traffic. The budget option requires the airport shuttle to Tri-Rail, then a transfer to Metrorail and finally trolley/bus or rideshare; expect around 1½–2 hours door to door, not a clever shortcut.
MiamiCentral (Brightline): From Brightline’s downtown Miami terminal, take the free Metromover to Government Center, then Metrorail south to Douglas Road or University; use the Coral Gables Trolley from Douglas Road for Miracle Mile. Allow about 45–60 minutes to downtown Coral Gables, plus a $2.25 Metrorail fare. For two or more people with luggage, rideshare is usually less fiddly and can be competitive.