I flew in there 2 weeks ago. I flew Spanhoe-Jersey-Perpignan-Son Bonet.
Customs are available, fax or email in advance. Ensure that you have all of the documents for the aircraft in a neat folder along with your passport and Pilots licence/medical.
Fuel and oil easily available but CASH (euros) or fuel card only. Sloane Helicopters have a set up there and the CFI Alistair is a very nice chap who can help out with any questions.
They will route you in via the NE of the Island at Pollencia and route you low level all the way along the motorway into Son Bonet.
Palma are not interested in taking you if you are a light aircraft and will automatically refer you to Son Bonet. All flights even local sightseeing require a FPL.
4 day stay cost me about 30Euros.
Well worth the visit.