Yes, both are acceptable, but the second form is far more common in everyday speech and writing. The Saxon genitive form tends to be more a feature of literature, journalism, holiday brochures, and so on.

Yes both are fine, but you would write, I go to Ibiza's discos. Do you go to Ibiza's discos. The s is added here because the discos belong to Ibiza. Do you go to any discos in Ibiza. I often visit Barcelona's top museums.

Both of your examples are acceptable.