Finally a post I might have an answer to.
I always love to visit Del Mano Gallery on Montana in Brentwood and
close by in Santa Monica there's Sculpture to Wear with modern avant
garde type jewelry. And a little further away, but still on the
Westside in Venice on Abbot Kinney is Altered Space Gallery. They
have a nice selection by Eric Silva, Todd Reed and others.
Freehand on Third (can't remember if it's St. or Ave.) near the
Beverly Center has some interesting things too, but more commercial.
Still like them though.
All of these are more art/studio jewelry as opposed to traditional
fine jewelry. You can always go right to Beverly Hills to see
gorgeous red carpet offerings.
I'll be interested to see other's recommendations. Always looking for
great jewelry galleries in L.A. myself.