Hi there,
some mums will say that they don't warm baby food up and I think that is probably a good idea but you have to get them used to it pretty early. I always warmed my baby food so here are my tips:
1. You could warm the food before you go out (in the microwave/in boiling water) and make sure it is super-hot. Wrap in tin foil and a cloth and put in baby-bag. By the time it is feeding time, the food should still be pretty warm. You could also transfer it to a thermal flask/container.
2. Ask a restaurant/bar/cafè to warm it for you if they have a micro.
HTH
Sinead