I use to live in So California and between the broken glass, shards of steel wire from people letting their tires wear down to the steel belt, thorns and the hellish Goatheads I had a difficult time finding a tire that would fend off that stuff. The best combo I found was a Conti Gatorskin, with a Mr Tuffy liner and a thorn resistant tube but with that combo I still got an average of 3 flats a week not to mention fragile sidewalls...that was until an LBS turned me onto Specialized Armadillo All Condition tires, from that time onward I got just 1 flat in over 13,000 miles and that flat only happened because I let the tire wear down to the cords. I used the Armadillo with no liner and an ultralight tube!
Since then Specialized changed their Armadillo All Condition tire to a lighter construction, I'm not sure how good those are now since I moved from Calif and no longer live on trashy streets and thus no wanting to try a heavier tire for no reason.
I do think the ultimate flat resistant tire is the Schwalbe Marathon tires, but they're heavy and expensive but will last a long time. I also think that today there are decent tires out there you can find that will work for less than Specialized or Conti. Bontrager makes the Hardcase which is very capable against flats as is the Maxxis Re-Fuse. But all around for a tire that isn't too heavy, lasts a long time, cost is reasonable I think is the Specialized Armadillo All Condition, this tire even has a tough puncture resistant sidewall, this sidewall is so tough I rode the one tire that I flatted which was on the rear for 5 miles FLAT, it did nothing to the sidewalls nor did any damage to the rim, whereas the Conti's sidewalls are paper thin and ripped with ease, plus the Armadillo wears better than all the tires except for the Schwalbe Marathons.
If you want a lighter tire you can do that but add a Panaracer FlatAway liner, this is the toughest liner of any on the market, I tried to drive a tack through a piece and couldn't do it but I could with relative ease with a Mr Tuffy, and my hands ached after trying to cut a piece of the FlatAway liner but cut the Mr Tuffy like butter.