Cala Llonga is a lovely resort - don't listen to that crap that it's just for Chavy Brits!
I went there a few years ago in the June with my mum, a couple of her friends and my wee cousin. The beach is lovely, a couple of decent restuarants, a few good bars but it is a fairly quiet resort, most of the entertainment is hotel based. There was one disco up a hill which was practically empty but my cousin and I had a great time. No clubs.
If you are after a nice relaxing holiday then go for it - however you should hire a car, the buses stop early in the evening but the taxis are cheap (thats how we got around).
The scenery around the small bay is fantastic and you can climb up the hills on either side to explore. There was a small fairground when we were there which was fun....
I would go back again defo. Have also stayed Santa Eulalia and San An and the Bay in my 9 times on the island.
I get sick of people slagging places off by generalising the types of people who go to them.
Go yourself and see what it's like. Everyones opionion is different.