We make a lot of trips down to Cabo to manage our condos at Terrasol and we must (like everyone else) get our Covid test to come back to the USA or Canada. We found the Saint Lukes testing location at the Cabo San Lucas marina to be the best priced location at only $18 for the antigen test and the PCR test was also very inexpensive. They take credit card too. The website for Saint Lukes at Cabo can be accessed here.
They advertise you can walk-in but still require to set an appointment at their desk so you should just use this link to schedule your appointment which is the QR code at their desk. Click this link to schedule your appointment.
Just go to the CABO sign at the marina (pictured) and walk down the corridor and you will see the Saint Lukes testing location which is open from 8am till 8pm (but they stop testing at 6pm). They will accept walk-in appointments without registering but you still have to register when you get there (even if a walk-in customer) by scanning the QR code at the desk. I suggested to them that they have this QR code available on the outside of the office so that people can scan while they wait. There are other Saint Lukes locations available around the Cabo San Lucas area, just go to their website and you can find them on their mapped locations. Good luck and safe travels!