Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Albuquerque to Guanajuato as you normally would.
Due to multiple factors, expect to potentially pay more when booking in December. For low rates, April can be a great choice for travel to Guanajuato. Flights to Guanajuato from Albuquerque in April are about $588 on average during April, but can be found for as low as $383.