I wrote back to say: "Hi Aarti, the easiest way to get to Estepona from Malaga airport is to take the dedicated Malaga airport to Marbella bus. Remember to look in the timetable at the column showing the winter departures column from the airport. This one way ticket on the bus costs just under €4.50 per person for the 45 minute journey.
To catch the Malaga airport bus to Marbella you come out of arrivals, turn right and about 50 metres along the pavement you will see the bus stop. You buy your tickets as you get on the bus.
When you get to the Marbella bus station, take the bus to Estepona, check through here on the Costa del Sol bus page for the Marbella Bus Schedules. Look for the MARBELLA - ESTEPONA route.
The ticket will be less than five euros so you can get from Malaga airport to Estepona by bus and have a cup of coffee in the Marbella bus station all for less than 10 euros!
I hope this helps you with your planning Aarti, have a good trip." Mike
PS: You can now do online bus ticket reservations through the gomarbella reservation system.