Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Jacksonville, North Carolina to Puerto Rico as you normally would.
Due to multiple factors, expect to potentially pay more when booking in March. For low rates, May can be a great choice for travel to Puerto Rico. Flights to Puerto Rico from Jacksonville, North Carolina in May are about $608 on average during May, but can be found for as low as $406.