I suggest you to stay as closer as possible to the festival, so Igea Marina or Bellaria (basically it's the same town)
2nd June is national holiday, so the prices will be high for the weekend, also for basic hotels and it could be really difficult to find cheap places.....I would avoid the festival camping, as if it will be in the same area of Bay Fest, it's really poor compared to festivals in Europe and with no shadow...
personally, I'm checking Camping Riccardo
I remember many years ago there were trains at night in the summer between Rimini and all the towns on the coast, but probably that weekend is too early in the summer, who knows...anyway, try and check https://www.trenitalia.com/en.html
otherwise there will be taxis, that in Italy are not as cheap as in other countries in Europe.
when inside the festival, keep in mind that in Italy most of the "Festivals" are basically concerts, so even if you have a single day ticket, once you enter the fest area, you are stuck there, with no possibility to go out and re-enter....so take as more booze as you can outside (there are some shops that sell at good price in Igea Marina)
that's all for now 馃槈