One family went to Cabo, then tested before their return flight to the US and ended up testing positive but asymptomatic. They tested 3 times and all 3 were positive.

The airline said they could fly based on the CDC’s guidance after 14 days isolation.

(instead of waiting 14 days) So, they ended up flying from Cabo to Tijuana, and then walked across the border (you buy a ticket to do so) and then flew home to Kentucky from San Diego. No one tested them during that process. Here is a pic of the airport so you can see the border and the sky bridge.