Everyone told me to go to San Andres. So I did.
San Andres is nice and has all the usual activities of a sun and sand vacation. Plus, San Andres has some decent restaurants and lots of duty-free shopping.
The only thing that I didn’t notice were too many spas. There was a spa on the beach. But as they appeared to be the only game in town, they only had 30 minutes massages available. They only had one massage table and it was separated from the public by a bamboo bead curtain (which was never closed). The main “spa” activity in the hut seemed to be the fish foot spa. Even with a reservation, we did not manage to get a spa treatment on the beach. We did find a hair salon that also had massages and manicures and pedicures.
Apparently, the smaller (less crowded) Providencia is much nicer than San Andres. Perhaps another time.