I am not trying to be sarcastic, but Costco has a nice selection of jewelry and good prices.

Costco is good.  Their quality is superior to franchise outfits like Kaye Jewelers, etc.  Personally, I use Unicorn in Rancho Bernardo, however, I have a friendship with the onwner, therefore YMMV, but the quality can't be beat - and don't be afraid to negotiate.  Deal with Fred, if possible (he's the owner).