Ibiza is predominately a Roman Catholic culture. All its 30 churches are Catholic. Other faiths do hold services in Catholic Churches which they borrow for the day but there are only two English Speaking Church Of England churches in Ibiza. Here is a website with more information www.theibizachurch.org. If one of the couple is Roman Catholic, then they are permitted to marry in any of the islands stunning 30 Churches.
Permission is required from both the couples local parish priest and the priest whose church the couple are marrying in. Its a slow and laborious process to have all the administrative paperwork in order for the wedding to take place but its well worth it in the end. This is an area where hiring people to process all the documentation is worthwhile as they know the system and the people to deal with. I have found Sam and Johnny Hocking to be good people to help with all the documentation. You can contact them here www.weddingceremoniesibiza.com
Budget about €800-1000 to pay the church and the priest for the paperwork, use of church and priests/ alter boys donation. A guide to mass times, contact details and pictures of all the Ibiza Churches can be found here. Please be aware that Priests in Ibiza move very slowly and may be conservative in their thinking, so expect delays and deal with them in a respectful and considerate manner. English may not be their first language either.