Thanks for posting on a message board... The Henry James Band is playing at the restaurant formerly known as Bella Luna. This is essentially the same band as the Rythmatics except one guy (Steve Keyes ) is in Mexico.
The group is well-known around the islands... you can see a live video here of one of their performances down at the port of Friday Harbor.
http://www.sanjuansites.com/rhythmatics/default.htmGood Luck!
Where are you traveling up from?