Thanks a lot for your suggestion. I was not sure if 'illusion' had that meaning in English too (as I'm not native in the English language), in the dictionary that I use they distinguish several meanings (http://www.wordreference.com/es/en/translation.asp?spen=ilusi%C3%B3n), and I thought 'dream' was more adequate here. But you are right, the meaning is more like 'false hope' or something like that.