Although Saffron is used in Spanish cooking (Paella) I believe it comes more from Hungary along with Paprika. I know someone will correct me if I'm wrong. Funny, I just made paella tonight, and used saffron that I got in Hungary. I used the America's Test Kitchen recipe and was quite pleased how it turned out.
Balsamic is Italian, from the Modena region. Recently I've been hearing that for most dishes, one could just use a "knock off". If you want it on ice cream, get the real stuff.
I'm going to Andalucia in a few weeks, and I personally will be keeping my eyes open for olive oil. I plan to bring bubble wrap or else use a certain type of cooler bag that I typically use for wine. Should it break, I think olive oil would be a real drag. . .
I do think its super fun to bring back food ingredients from my travel, but I do know I can get similar at home. I do like the vanilla my friends bring home for me from Mexico.
I have brought home my share (and more) of wine and cheese from France and spices from Hungary. I ALWAYS am very forthcoming with customs. It is just not worth it, otherwise. Strange thing is, I think each person is allowed 1 1/2 bottles of wine. We have brought back a bit more thinking that we typically have wine that we love that we purchased inexpensively. If we have to pay 5% duty, so be it. But when I say, "some wine", they never ask, "how much". Sadly, I guess I'm not that interesting. . . I would be VERY careful about meats and it is my understanding that fresh produce (for good reason) would never be allowed.