I have stayed near Cala Gracio twice, and will be staying near there again this year.
I definately think it is on the better side of San Antonio.
Cala Gracio is quite a small beach itself and can get really busy in the height of summer, however you get a much nicer crowd at Cala Gracio than you would down on the main San An beach. It's quite popular with families.
Also just round the cove is another little beach called Cala Gracionetta which has a nice little restaurant (which apparently serves really nice food, have never eaten their myself though)
I reckon it would take you at least 10 minutes to walk down to the Sunset Strip and about 25 mins to walk to the west end. Although it is fairly close to the dreaded West End it is very secluded from all the hustle and bustle.
I really liked Cala Gracio and I am looking forward to going back.