Local control cities seem to be preferred for some routes (i.e. why 60 is not signed for Indio until Riverside) - CalTrans practice tends to emphasize the nearest major destination first, before any longer-distance ones. (i.e. Route 85 is signed for primarily Gilroy, not Los Angeles, southbound)
Only exception to this is the usage of Sacramento for 405 and 170.
Sacramento is seen on 210 as well for similar reasons.
California has a special aversion to out-of-state destinations (Blythe or "other desert cities" before Phoenix, despite Blythe having no appreciable population, certainly not anything giving rise to a need to sign it from 200 miles away) and as for international destinations, I can think of some distance signs for Ensenada and San Felipe, but as for an actual control city... Caltrans would rather leave it blank, as in the case of 805 southbound, which could certainly be signed Tijuana, BC.
That's what I mean, is Sacramento is signed on 210 Westbound on Mileage signs atleast and that's for I-5 north, yet East bound 210 isn't signed for the next major city along it's parent route I-10 where it is headed.
Also I think in regards to control cities, in California they base it on traffic counts and suburbs. That's why on CA 14 north Palmdale and Lancaster are listed or Pomona on Ca 60. I think on the 60 it's because of it being the Pomona freeway and that most traffic headed out of Downtown Los Angeles seems to not be headed to Arizona.
One thing to note though is Indio does show up on CA 60 east, so why not have Indio on 210 East in San Bernardino.
Interesting difference between Los Angeles and San Diego control points.
I-10 East, San Bernardino
I-5 North, Sacramento (only far city)
I-5 South, Santa Ana
US-101 North, Hollywood/Ventura (probably to avoid people using 101 to San Francisco)
CA-60 East, Pomona
I-5 North, Los Angeles
I-15 North, Riverside
I-8 East, El Centro (Yuma is mentioned on a couple mileage signs)
I-805 North, Los Angeles