Good idea on the food allergy card, though I agree with dhammer that sometimes people don't care. I remember when we were in an italian restaurant in Madrid and I want to make sure my order had no dairy in it (I am extremely allergic). After asking in both English and Spanish (I am pretty much fluent) I felt convinced there was no cheese, cream, etc.

Sure enough, after taking a bite or two of my entree it became quite obvious that there was cream. So when our waiter came back out I asked again if there was dairy and he said there was. Now why on earth would he tell me now and not before? I think as mad as I was my parents were even more so. Though they don't speak spanish their anger had its own universal language!