Due to multiple factors, expect to potentially pay more when booking in April. For low rates, May can be a great choice for travel to Moab. Flights to Moab from John Wayne/Orange County in May are about $339 on average during May, but can be found for as low as $196.
Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from John Wayne/Orange County to Moab as you normally would.