The cheapest way from Guadalajara airport to city center is by bus. You will have to walk outside the airport to Chapala Road to take the bus from Guadalajara airport to the city center. The buses leave from the airport to downtown every 10-15 minutes. The bus fare from Guadalajara airport to city center is 12 MXN which is less than $1 USD. You can pay by cash to the bus driver. The bus travel time from Guadalajara airport to city center is around 45 minutes. However, airport ride-share services are much more efficient. Shuttle GDL busses will drop you off directly at your destination.