I found that there were actually TWO erratas in Diario Oficial.  We only have the first one:
http://dof.gob.mx/nota_detalle.php?codigo=5127480&fecha=06/01/2010

But also there was a second:
http://dof.gob.mx/nota_detalle.php?codigo=5135357&fecha=13/03/2010

The change is in bold in the second document, and clarifies that the entire municipality of Ensenada follows US rules, not just the city of Ensenada.

I'm not sure what this means with regard to San Quintin, but if it's following the letter of the law as currently written then it would currently be following US rules, and later when it officially becomes its own municipality then it would follow Mexican rules (unless they later change this).



Date: Sat, 10 Oct 2015 09:24:36 -0400
Subject: Re: [tz] America/Santa_Isabel
From: arthurdavidolson@gmail.com
To: mj1856@hotmail.com
CC: eggert@cs.ucla.edu; gregsla@microsoft.com; tz@iana.org

Radio station XEQIN of San Quintín has a web presence:
    http://ecos.cdi.gob.mx/xeqin.html
It's a daytimer, the web page says it broadcasts from 5:00 a.m. until 7:00 p.m. Streaming wasn't working for me today here in Maryland until shortly after 9:00 a.m.; I'm now (~9:15) hearing a Spanish-language announcer who has mentioned the date, meaning it should indeed be a live stream. I haven't yet heard a time announcement, and I'm surprised the streaming started at 9:00 my time rather than 8:00 my time.

We'll see what happens in the coming days and weeks--in particular between October 25 and November 1. (If nothing else, we may produce a spike in XEQIN's ratings.)

    --ado

On Fri, Oct 9, 2015 at 8:02 PM, Matt Johnson <mj1856@hotmail.com> wrote:
+1 for America/San_Quintin.   Thanks Greg.

Also - and you guys are going to love this - I looked up the coordinates we have for America/Santa_Isabel in zone.tab, which are +3018-11452, and look what I found:


 
 


We've picked "Sierra Santa Isabel" - a mountain range.  :)


Nowhere near the actual town of Santa Isabel either. 


> To: gregsla@microsoft.com; tz@iana.org
> From: eggert@cs.ucla.edu
> Date: Fri, 9 Oct 2015 13:31:56 -0700
> Subject: Re: [tz] America/Santa_Isabel

>
> On 10/09/2015 10:47 AM, Greg Slayden wrote:
> >
> > I see conflicting information online about when DST ends there, either
> > November or October. Making contact with locals in that area is likely
> > the best way to find out
> >
>
> Yes, if we can establish that San Quintín uses Mexico's DST rules, we
> can effectively replace America/Santa_Isabel with America/San_Quintin.
> Normally we'd prefer Lázaro Cárdenas as it has more people, but it's an
> ambiguous name whereas San Quintín is not.