I think you have to catch a bus to Ciutadella and then one to Cala Galdana.

Thanks for that jeffers, is there away to get a bus timetable from the internet.

This is possible, I did the reverse, but you will need two buses the 'Torres' bus Cala Bosch - Cuidadela, and a 'TMSA' bus from Cuidadela - Cala Galdana. However there are two corresponding bus stations in Cuidadela 10-15 mins walk apart...

http://www.e-torres.net/ingles/index.htm

Click on 'Show Location Map' will give you a map of where both bus stations are in Cuidadaela, (Bus Playas-Bus Mahon).

TMSA buses.
http://www.transportesmenorca.net/horario.htm

Thanks for the information Ouzo, how long does it take and whats the journey like. Thanks again