You know, I don't know.
I'll check it later when I get to the store.
I don't think its very high though - most of SoCal has pretty good water. I get the occasional farmer or other urban dweller who had a well, and I call tell the difference right off.
Depends where in southern california you are.
Colorado Water is high is TDS typically 500 to 700 mg/L
Northern California Water (State Project Water is better), typically around 300 mg/L.
The LA water from the Owens Valley is very good. (about 150 mg/L TDS)
Some of the well water can be very good or very bad. The goundwater in the Chino / Ontairo / Corona area is very high in nitrates from all the cows in the Norco area. Normally it has to be treated (ion exchange and/or reverse osmosis) before distribution.
In comparison, most surface water from the east is around 100 mg/L.