Renting from the airport is your best bet! There are plenty of car rental services. There are also taxi services. To take you to and from the airport
You can exchange your money at the airport! Or you can exchange it at the local bank in Ajijic. But airport would suggested.
Calle Hermengildo Galeana 43 45920 Ajijic, Jal. Mexico!
There is no specific dress code! The weather will be sunny and bright and cooler into the evening.