Hello,
I've read recently that the main language spoken in Ibiza is Catalan. Would this mean that if I try Regular Spanish I won't be understood ??
By the way, what percentage of Ibiza people speak english ???
Regards,

???? Where did you read that?
English is spoken on Ibiza more widely than Spanish nowadays. You'll be fine.

OF course you will be understood! Where did you hear that nonsense??.
In Ibiza, as well as in the whole Balaric Islands, both Catalan and Spanish are spoken, and I will go further, Spanish is more widespread than Catalan

Despite what the Catalonian regional government would like you to think, the reality is that Catalan speakers know that it is completely unrealistic to expect the entire world to learn Catalan to speak with them, so everybody learns Spanish. If Catalan speakers want to do business with, say, Argentina, I guarantee you that they know that there is no chance the Argentinians will learn Catalan just to get the business. Everywhere where Catalan is spoken, the people will speak Spanish. Your accent will probably give you away as a foreigner anyway, which will mean that they will not expect you to speak Catalan and will speak to you in Spanish with no problem.