Have no fear, Catalina Ciriza! There are probably between 50 - 100 cybercafes in BOTH Madrid and Barcelona. You probably won't need your laptop at all unless you want it for work while there.
It will be difficult, I believe, to write the email on your laptop and "upload" that email at a cybercafe FROM your laptop. Maybe I'm wrong and maybe things have changed since I used the Madrid cybercafes last (in October 2000).
I know that easyEverything has 2 cafés in Barcelona and one in Madrid. View their website @
http://www.easyeverything.com . Most all the cybercafes are pretty cheap.
You might do well to set up a free web-based email account with either
Yahoo or
Hotmail and set your POP settings to receive your home/work email through that same account while traveling. This is what I do.
Have a great time! Saludos, MadridMan