US keyboards have some of the keys mapped to different characters, the @ symbol (if I'm not mistaken) is above the number 2? On a UK keyboard you have it over beside the # and <return> keys. a US keyboard doesn't have a "£" symbol either so try installing with a UK keyboard or it'll just become irritating. You shouldn't have to select a setup like ASCII or whatever usually.
I don't know about the debootstrap program so can't comment on its use.