My mac ibook 10.4.11ppc and when I cha...

To change the language from Spanish to English, visit System Preferences / International / Language. If English is not the language at the top of the list, drag it to the top of the list. Then click the Input Menu tab and make sure that only "US English" is checked.
Sorry if you already knew that, but I have no way of knowing what you know or what you already did.
If this doesn't work, go to System Preferences / Accounts and create a new temporary user. Log out and then log in as that user. If that account comes up in Spanish, set it to English. If it goes back to Spanish, you probably ought to reinstall your OS, using Archive and Install. If the new user stays in English, you have some problems with the individual account settings in your main account. I suspect some preference file, such as ~/Library/Preferences/com.apple.systempreferences.plist, is corrupt and should be deleted (warning: deleting this file will set a lot of your user preferences back to system default). You can use the freeware application Preferential Treatment to find obviously damaged preferences, but it will not find all types of damage.