Rather than just getting a taxi, another, perhaps more interesting, way of getting from Malaga airport to the villa in Calahonda is to combine rail travel with taxi. It is certainly cheaper than taxi alone which could be about 48 euros.
The train station is an easy 5 minute walk from the departures hall (salidas) which is on the floor above the arrivals hall (llegados). Turn right on leaving the departures hall.
Trains leave every 42 minutes to Fuengirola for which a 4 zone ticket costing 1.60 euros per person is needed. This can be purchased from the machine on the right just before ascending to the platform. It accepts notes and gives change. It may also be possible to buy tickets on the train, perhaps at greater cost.
On reaching Fuengirola leave the station, turning left to the taxi rank a few metres away. The fare to the villa in Calahonda should be about 15 euros.