Do not drink the water in mexico, bottled is cheap and look for a screw top cap 5 gallon jug. Use one of those blue inline filters to fill your tank, most parks do not have enough pressure for direct hook up. The filter will keep sediment out and give you some sterilization in case you swallow shower water. i use hydrogen peroxide as a disinfectant as well. I simply empty my tank when back in the US and give it a good dose of chlorine & empty again. Fuell is not an issue, there is only one stretch you have to worry about and that is the section south of Mazatlan to the San Blas turnoff, and I noticed last year they were constructing a new Pemex station along there.
Is your truck diesel? If so you may have a problem. No ULSD. 2013 & 2014 are far more sensitive than 2007-2012 where people get away with ignoring it. You will have to find someone to bypass the fuel filter, etc and that will affect your warranty. USLD will not be available until late 2015 at the earliest, probably later.