I forget the name of the park outside Puebla. Is it Las Americas? A 6 unit Caravan pulled in and I had to unplug as the voltage dropped below 90.
We were at Las Americas a month or so ago. I used my tester and found all the wiring in the area toward the street is incorrect. They said we could park behind the wall where the houses are so I tested there and found one good outlet so that is where we parked.
Many other parks have bad wiring but few RVers ever check. Most just plug in assuming all is AOK. At the place many use in Matehuala I found only 2 outlets properly wired.
We were recently in another place where many outlets were incorrect so I helped them figure out how to rewire everything. It often starts right at the entrance panel and continues on through the system.
Many parks use inadequate wire size and make runs too long to reach more spaces. The amount of power that can pass through a wire is limited by the size of the wire - and every foot of wire adds more resistance so the amount of power is reduced as the wire continues on to more spaces.
This all adds up to more risk in RV parks in Mexico and all travelers should be warned of this and precautions should be taken to protect your equipment. The devices mentioned previously in this thread are needed in Mexico but we also use them in the US and Canada as we have found bad wiring in some places in all countries - though odds are increased in Mexico. Check the outlet with a tester. Use a surge protector. If possible use a voltage regulator. They all cost money but so do the systems we need to protect in our RV.