Milk is apparently the winner. Here's a link to a page that explains spiciness and the antidote to it:
http://www.fiery-foods.com/dave/taste9.html
The active ingredient in hot peppers is a chemical called capsaicin which binds to the taste buds and causes all that wonderful pain. And "bind" is the word -- it doesn't go away quickly. But casein, a protein in mix, can "unbind" the capsaicin from the taste buds. To quote the article:
"Scientists now believe that casein in the milk is responsible for its cooling effects. According to Robert Henkin of The Taste and Smell Clinic in Washington, D.C., casein is a phosphoprotein that acts as a detergent and strips the capsaicin from the nerve receptor binding sites in the mouth which are contained in the taste papilli. The casein in milk is in the form of calcium caseinate, which constitutes about three percent of milk. Other possible cool-downs containing casein include milk chocolate and some beans and nuts.
The article goes on to talk about how quickly milk calms down the mouth, and gives an average time of several minutes. But in my personal experience, it has worked faster. I'm not a fan of hot Mexican food, but I do like hot Indian food, and Indian cuisine comes with its own "de-spicifying" dish: raita, a thin yogurt/cucumber soup served cold with many meals. A sip of raita almost instantly tames the heat from the fieriest curry. I wonder if yogurt is a better cure for heat than average milk -- it might have more casein in it, being a semi-solid, fermented product. Or maybe, being somewhat thick, it coats the mouth better than milk. Yogurt is also easier to digest for those of us who are older -- and with milk, the ability of many people to digest it takes a real nosedive somewhere in the 20s.
So if I were you, I'd keep a little yogurt nearby as an antidote.