When my son was still taking formula, as we were transitioning from breast milk to cow's milk, he wouldn't drink anything that wasn't warmed (we found out later that he had severe acid reflux, and the warmth was probably soothing to his poor little throat.)
If you have a warm-only drinker, here's a few tips for on the road situation. Babies R Us sells a warmer that you can push activate. It only works once, its kind of like those hand warmer dealies (come to think of it, a few of those would probably work too.)
Also, I found that requesting a cup of hot water at a restaurant (or on an airplane) would work too. You could either add a bit of the hot to the bottle, or, if you would prefer to use only bottled, you can actually sit the bottle of formula in the cup of hot water. (Just be careful about melting or making it too hot since they serve tea water at a scalding temp. sometimes.)
Safe travels.