Originally Posted by David-A

If you don't have luggage you might as well take the bus into Malaga city centre.
Or alternatively take the train (due to construction works the walking route to the station platforms is changing a lot. I think currently you still get routed through the car park? Anyway, this could be quicker than the Bus and with less ambiguity about where to get off.

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I have no idea if the gallery at the airport is open on Sunday afternoons - they appear to work to their own hours.

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Obviously there are 3 or you which makes taxi costs more reasonable, but you could probably reach your hotel by public transport relatively easily if you wanted to by either:
(a) Express bus from Airport to Marbella bus station, onward bus to Estepona
(b) Train from Airport to Fuengirola, onward bus to Estepona.
(c) Go into Malaga city, take bus to Estepona. But I wouldn't do C! Do A or B depending on bus timings.

Alternatively you could take the express bus to Marbella bus station and just take a cheaper taxi from there to the hotel.