There are 3 buses that leave Fortaleza daily heading to Jericoacoara (they drive by Prea, which is 12 km before getting to Jeri).
The bus line is called Redencao, it has 2 types of service, the Executive and the VIP. I believe it's the same bus (they all have A/C, TV and toilets on board), the difference is that the VIP hardly stops during the trip (5h45 instead of 6h30 to 7h00). The buses drive to Jijoca and you then switch to a 4 x 4 bus for the last 30 minutes. If you want to get off in Prea, make sure you tell the driver or assistant when you get onto the 4 x 4 bus.
Executive schedule, leaves Fortaleza at 09:30 and 17:30, the price to Prea is R$ 31,50
VIP schedule, leaves Fortaleza at 15:30, the price to Prea is R$ 50,00
You can also get private 4 x 4 transport to drive you straight from the airport to Prea for R$ 400 (up to 4 people).
Or a ktiesurfari / downwinder with professional drivers for R$ 700 per day, up to 5 people.
PM if you need any more info.