Some countries in Europe you can just find a cheap SIM card at a convenience store. It’s worth it if you know you will be somewhere for at least a couple weeks. In Dubvronik, we found one for 108 kr which is only about 13$ for 5 GBs of data.
We stayed at a hostel called Villa Banana that was $20 per night. It was about a 20 minute walk down to the old town. It was a really nice hostel with the nicest owners ever. We had the best view of the sunset at night.
Down in the main port you can find ferry boats that go to the different big islands. We took a ferry to the port of Sobra on Mljet island. Or you can take a day trip to Lokrum island which runs every 30 minutes out of the old town port.
There are a bunch of areas where you can go down to the beach and lay out on the rocks and take steps down to the water.
Banje beach is the main beach on the island. It’s one of the bigger ones and you can rent umbrellas and order drinks.
The old town is really cool and they filmed part of Game of Thrones there.