Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Guatemala City to Liberia as you normally would.
Due to multiple factors, expect to potentially pay more when booking in May. For low rates, September can be a great choice for travel to Liberia. Flights to Liberia from Guatemala City in September are about $585 on average during September, but can be found for as low as $324.
It’s generally more expensive to depart on a Thursday, if you have to leave on this day you can still search on Cheapflights to find great options that meet your needs.