First of all I would like to thank everyone who gave me tips.
Our call on Ibiza was delayed for two hours as the cruise ship berth was occupied by a ferry and our ship cannot get into the port.
So we decided to go ashore after an early dinner.
RCI took 6 USD per person and way for the transfer.
A taxi to the main square was about 10 EUR one way.
Everything is there to walk so here are some impressions from our night walk from Eivissa - or better know as Ibiza City:
Hasta la proxima!