C´mon!
Use your common sense, and don´t let be driven by TV news or fear!
I live in Cancun. I vape all around. Walmart, Home Depot, malls, restaurants like Tycoz (you should try it! Very yummi baguettes), VIPS, Sanborns. At first people just turn around and they just keep looking the lighted led (if it´s red or orange) and when they do you can just perform a little theatrical moves like puffing a little more and putting it in your pocket, they get very confused by this.
When you disassemble the battery from the atomizer, or when you explain it is not hot ash and put your finger in it and you don´t get burn at all, then they get curious about the ciggie. You can give then a demo.
Your concern about mexican customs or airport check-in, it´s very simple.
In your handbag or backpack, (the one you keep with you when you get in the airplane), just place a little bag containing your bathroom stuff (toothbrush, toothpaste, deodorant, some makeup) AND include some regular pens. With them, include your fully assembled e-cig. About your e-liquids, just take away the labels. Use your common sense and just carry 1 little bottle with you. The rest of them, put it in the big suitecase with the clothes. Or just don´t bring them all, just the little one, and give me a call, I will sell you some.
The police can´t detain you for using it in public (Most of them doesn´t know what that "thing" is anyway). Don´t be afraid to get out of your hotel to get a walk, and enjoy downtown. It´s not true that narcos and police just shoot each other in every corner. They shoot, it´s a fact, but in places you shouldn´t go. It´s like if I would go to NY, and then ask to the taxi-driver: "Take me to the heart of the Bronx".
You can get a cab and ask to be driven to downtown, Av. Tulum, to the "Ayuntamiento".
This place is totally safe for you and offers restaurants, Ultrafemme, etc.
Around there it´s an italian restaurant you should try, called Rolandi´s.
Then you get another cab, and ask to be driven to "Plaza de las americas". It´s a mall where you are going to find some fun!
Then, when you can´t walk anymore because your feet are sore, get another cab back to the hotel zone, where your hotel room is waiting for you.
I hope this helps a lot of afraid american people.
And I hope you pay me a visit!