Croatia is great, very hot in the summer, and quite balmy in the spring and autumn.
Best nightlife I found is in Zagreb, the capital, however, it's not really very relaxing, but anywhere down the Dalmation coast is gorgeous, full of Roman ruins and has the odd night club floating around.
My favourite town was Dubrovnik (the Latino nightclub is ace, is a touch cheesy!) closely followed by Split, although for beaches you're looking at more lounging around on rocks next to the sea than anything else.