We want to end up in Kino Bay, an hour west of Hermisillo. We have been before and into other parts of Sonora with no problems, so the only issue is whether or not one can find ultra low sulfur fuel. Thanks for the reply, let me know if you have any info on this.
I would also warn you that the chief of police in Tecate, MX was killed last week after only four days in office. The chief of police in Tijuana was killed last night. 8 people were killed last night by gangs in Tijuana, several of which were police officers. And an attempt was made on the life of the chief of police in Rosarito. If you are thinking this won't effect you because they were all gang related or political related, I would add that innocent victims were killed in the shoot out last night, including a 13 y.o. girl. Basically they don't care if you get caught in the cross fire. They are also looking for U.S. citizens to kidnap in order to extort money and rob. I heard a woman make a report in San Diego who was gang raped by four men in her RV in Baja California.
After hearing all of this, should you decide to go ahead and travel to MX I would advise you to stay away from the west coast and travel as far east as possible. Take toll roads and stay away from the free roads. Try to travel in a group and park in a circle with your doors facing inward. Caravans have been held up and robbed though in the past. Try not to park in parking lots but in areas that you are already familiar with. Oh my goodness, I can't believe you are still considering this...but it is your choice.
The only problem with Mexico fuel is that you can't rely on the supposed reports. What is on the sign isn't necessarily what you are getting. Last year several gas stations were shut down in Mexico and investigated for fraud, pumping less gas to the customer but charging more. Further, it isn't the purest gas so it will burn a lot faster than U.S. petrol will. There are a lot of additives in it. So no, you can't rely on or plan on low sulfur fuel being available all the way down your route to Sonora.
With that said, be wise, be safe and I Vaya con Dios (Go with God) You're going to need Him.