Ios is known as a party island. Most (but not all) people who go there will be looking for the nightlife but it is also a very pretty island and has great beaches.
fantastic place with the best beaches in the cyclades islands , it has brilliant nightlife wether your 18 or 58 this is the island of paradise ,from a busy beach at myloportas to little coves scattered all round the island where you can have a beach with golden sand all to yourself
You have 3 choices. Down in the port, up the hill in chora which is where the nightlife is or over the hill down the bottom and stay on mylopota beach which is pretty quite at night which might suit you.