Hi Ann22,
If you live in the US you only need an Antigen Test, Mostlylost has already replied to your question.
I am from Canada and require a different type of test, PCR, which is more expensive and takes time to get the results.
I would go along with the suggestion......Go Lab in Riberas. Another Lab you might try is Chopo Lab in Ajijic. 376-688 1212 or Best Labs 376-688-1174. Good Luck.