I was there a few years ago, and if I remember correctly they have a unicom type frequency, the locals generally speak in Spanish, and you just make blind calls in English and keep a good lookout.
There is a small office with armed police, so it is probably worth making sure that they are expecting you.
They are somewhat used to the English as Sloane Helicopters have a training school there - they would be able to give you some more information as they are generally very friendly - links below:
Sloane Helicopters
Sloane Mallorca