To get the @ on a Spanish keyboard, you need to keep the "alt" key pushed, and sequentialy push the "6," then the "4."
The really nice thing about the Spanish keyboard is that you get accents, ¿, and ñ for free!
The internet café in Orosí - at least most of the computers there - let you change keyboards with a click of the mouse. REALLY NICE!
Update: the ¨at sign¨ is actually known as the ¨arroba¨ in Spanish :)