When traveling abroad to stay in Miami accommodations and lodging, you should always have medical and travel insurance when in Miami in case something happens to you while you are away (getting hurt, falling ill, cancelled flight, lost luggage or having to return home earlier than expected due to the death of loved one).
There are many insurance companies out there that provide coverage at various rates and conditions. Airlines and travel agents can present you with options for travel insurance when in Miami. Even your credit card can provide travel insurance when in Miami.
Please be aware that health care costs are very high in the US and if something happens to you, bills may add up very quickly. That's is just one of the many reasons it would be convenient to stay in affordable Miami accommodations and lodging.
In any case, please look for information with you insurance provider to check conditions and coverage rates.
If you are a US resident, it is not necessary to subscribe for travel insurance when vacationing to stay in Miami accommodations and lodging.