There are plenty of marinas, but they are seriously expensive and often full in high season, and in 2011 we only stayed in one (Ibiza Magna in Ibiza harbour) for 2 nights because we had a visitor not used to rough cruising. Ibiza Magna has no toilets or showers, and highly priced undrinkable water. But it quoted a lower price than the other marinas in Ibiza harbour, and is right in the centre of the town.
In 2012, after leaving our winter quarters in San Carles, we avoided marinas in the Balearics altogether.