Fortaleza's airport is in the city, so taxi rides aren't too dear and public transport is also available.
Stay away from Natal, though. The new airport is useless and since its construction for the world cup they have not managed to put in any reasonable public transport option. A so called 'executive bus' has been promised on the port's web page for years as coming 'in breve', but as long as the taxi syndicate pays off the right people this will never happen.