Unfortunately Cala Llonga has been ruined by the All Inclusive, making the roads nigh on near dead! However, that said, there are many(including us) whom return more than once a year, year after year after year.
A beautiful beach, with some nice beach bars/cafes.
In the evening, to eat without doubt is Los Albatross. Best food by far and also a lovely relaxing bar just to drink. Opposite is Bar madison, whereby you will instantly feel at home. Chatting to both locals and tourists alike into the early hours.
When you familiarise yourself, take the road to the bottom (dead end) turn right and continue along the lane for about 10 minutes. You will come to another bay, Sol den Serra and a bar (Amante) that opened a few years ago. Very nice indeed!
Yes you will need to visit St Eulalia, it too is lovely and nice early evening.
Enjoy, as Im sure you will.