Mexican Pinguicula require what is called a dry dormancy; this has a similar timescale to a venus fly traps wet dormancy however the plants behaviour is different. During dormancy mexican pings stop producing carnivorous leaves and instead grow thinner, differently shaped succulent (non-carnivorous) leaves that stack onto eachother. It does very little growing, as well.
To induce a dry dormancy you need to gradually decrease photoperiod, prey levels and watering; temperature decreasing isn't such a big deal with dry dormancies but it won't hurt at all (as long as temperatures don't drip below freezing).
Please remember that the plant shouldn't die back during this time. Here's a link to an article regarding mexican pinguicula dormancies:
http://www.greyspinguiculagarden.com/me ... icula.html
On a side-note, Warm Temperate Pinguicula are tropical and do not need a dormancy period; that may be where the confusion lies. Good luck!
