Getting to Barra de Potosi

Perfect. Thank you, ZR.

By the way, when I pay the combi driver, does that include the transfer to Barra de Potosi at the airport?

No, it does not include a transfer. However, the fares are extremely low. It is a good idea to carry as many peso coins or MXN$20 or MXN$50 pesos bills as you can. It is a bad idea to hand the driver a MXN$500 or even a MXN$200 pesos bill. (MXN$100 pesos bills are not uncommon but not ideal.) I have never seen anyone try to use a US or Canadian dollar or any other currency. I don't believe it would go over well.

An added perk of using the combis is the opportunity for potentially practicing your Spanish. Part of combi culture in Zihua is to greet your fellow passengers with a "Buenos dias," "Buenas tardes," or "Buenas noches" when climbing aboard. Likewise, a salulation is done when leaving. It leaves open the ability to strike up a conversation and practice Spanish.