Hello and welcome to IYNO!
Ive never been to Malta but Id love to visit, my friend was there just last week and he loved it 
In Croatia I believe there are plenty of nude beaches...?
Oh yeah, also many nudist camps, the biggest are Koversada and Valalta. I go to Valalta every year as well as some other members from the forum, and I love it, you should definitely visit for the summer :)