The shuttle will pick you up from the airport. They drove me straight to the the clinic.
Afterwards the will pick you up and drive you either to the airport or to your hotel, if you are staying anywhere other than next door.
Going back across the border the shuttle will have a medical pass that should bypass a large portion of the line.
Yes, you should have your passport. Others have made it across with birth certificate and ID, but I wouldn\'t risk it.
Entering Mexico is a breeze. You just drive on in. No stopping, no questions. Coming back, if they ask, just tell them you were seeing a doctor.
I paid for my procedure in cash.
Also, you will not pay the driver for the shuttle service, you will pay the office. But keeping a little cash for a gratuity is nice.