When I used to live in SoCal I ran the thicker "thorn proof" tubes. And I don't mean those flatless solid foam style tubes, I mean the ones that are just made out of thicker rubber.
I've used tire liners before and learned to not like them. They're a hassle to change a flat with, they tend to slide around to the sides after awhile, and assorted other stuff I've seen while changing tires and tubes that people being in to the shop I seasonally help out at.
Good tires, good tubes, both help a lot.
It really comes down to your personal commute route and how you ride. If tire liners work for you then more power to ya. The only way to really know if to give them a try.
edit to add:
http://www.sheldonbrown.com/flats.html
Talks about the thorn proof tubes and also some about tire liners.