Landlords in Coronado are used to lots of military families renting their properties. Military families usually get two or three year leases. I really don’t think you will have any trouble finding a longer lease.
Rental prices went up a lot last summer. This was partially caused by the fact that all occupants of the officer housing on the Naval Amphibious Base were moved out so that that the houses could be torn down and rebuilt (there will be more than were there before). All those people flooded the rental market at the same time.
Winter is the best time to look for a house to rent in Coronado.