We travel to Mexico yearly and have never had an issue with any liquid medications. I make sure that they are in a separate ziploc baggie the same as here in the US and tell the screener about it. I don't travel with the ice packs because they are difficult to get re-frozen at times. Instead I use ice in a baggie and if they make me dump the ice (I run about 50/50 in Mexico) I can just get more once we are through the screening.
One year I had to dump the ice when I was screened, got some at a restaurant and then had to dump it again right before boarding. Unlike in the US, in Mexico any liquids bought after going through security are not allowed on the plane...you will go through another screening right before you board. It wasn't a big deal, as my spouse just went and got more ice from the flight attendant.
My experiences in Mexico with security at the airport is that it is pretty random and what is allowed one time won't be allowed the next time and vice versa. A lot of it depends on the individual screener. But I have never, ever heard anyone say that their liquid prescription medications were taken and I participate in a lot of different boards based in Mexico. If it were to happen, I'm pretty sure that people would post about it.
Have fun! We love Mexico and its people. Our favorite spot to vacation.
