The route finder at ViaMichelin.com gives the distance as 64km. The official taxi fare table indicates that this should cost around �53 during the day (or about �10 extra at night or weekends):
http://www.aena.es/csee/Satellite?cid=10488589 47333&pagename=Estandar%2FPage%2FAeropuerto&SM O=1&SiteName=AGP&p=1048858947201&c=Page&MO=1
The Thomas Cook Rail Map of Europe shows that there's no line to Monda (or anywhere nearby).
Buses to Marbella leave the airport at these times, daily:
0615, 0800, 1015, 1200, 1345, 1530, 1715, 1930, 2115, 2300. The journey time is 45 minutes. The fare is �4.03.
From Marbella, services to Co�n (which my map suggests will probably pass through Monda) leave at these times, daily:
0900, 1045 (not Sundays or holidays), 1330, 1630, 1800 (not Saturdays, Sundays or holidays), 1930. The journey time to Co�n is 1 hour 15 minutes, with a fare of �2.79.
There are also services to Oj�n (from where you could probably get a taxi) at these times from Monday to Saturday:
0700, 0800, 0945, 1330, 1445 (not Saturdays), 1600 (not Saturdays), 1815, 1915, 2115. The journey time is 30 minutes. The fare is �1.15.
http://www.ctsa-portillo.com/ima/pdf/marbella. pdf
Chris