This is a highly personal, subjective response but here goes...
I cook paella at home and have eaten it many times in Spain and the Canaries so can at least speak from some experience. It's not possible to get a good paella anywhere, short of paying lots of money. If you find a place that serves good paella at a sensible price then tell everyone about it cos you're real lucky to have found it. Mallorca is no exception to this rule.
Paella was originally a "peasant" dish and is now sold as a "tourist" dish in all the restaurants I've tried.
Good luck.

I have tried paella in many places in Cala Dor over the past few years and I think that the very best is at Can Trompe, which is one of the oldest Mallorquian restaurants in Cala Dor. Its a lovely restaurant in a great spot in the centre of Cala Dor - great for sitting outside on a warm summers evening and people watching. I like the mixed paella and the seafood paella, and if you dislike having to deal with bones / shells etc., for a euro or two more they will do a Blind Paella, without bones and shells. The portions are geneorus - I always take some home! You have to order for 2 as a minimum usually but I think that there is often enough for three. With a large party I would order 3 portions for 4/5 people.
Hope you enjoy!

I agree with Marymary - lovely restaurant in a lovely spot to watch the world go by - roll on August!!