For travel outside the US, the current requirement is having a negative Covid test within 72-hours of your return flight back into the United States. Here is the link to current CDC guidelines with FAQ's for airline travel:
Many resorts in Mexico and the Caribbean are offering free covid testing prior to your return flight as well as options for quarantining at or near the resort for up to 14 days if you test positive. The list is extensive so please contact us for more information.
As vaccination levels increase, the requirements for travel may change to include proof of a vaccination. We have seen this possibility required by cruise lines once they start operating. As there isn't a standard requirement yet and regulations change daily, please contact us for more information.