If you look on the CD they should be there. I have an Australian version but i have languages for France, Germany, English (Of course), Czech, Hungarian, Polish.
English should be on almost all versions of Crysis as the game was made in English.
If you do have the English pak it will be located in the first directory of the CD (D:\)
It will be under English.CAB. Extract the files, english.lng and english.pak and place them in the crysis localized directory.
Eg: C:\Program Files\Electronic Arts\Crytek\Crysis\Game\Localized
*If you do have English on the CD you wont have to copy anything as it will already be in the directory you will just have to do the step below*
EDIT: Almost forgot, in the Localized folder there will be a file named "Default.Ing", Open it with notpad delete anything in there and replace it this this.
Code:
Language = "English"
PAK = "English.pak"
If you do not have the English pak on the CD like Koala said we wont be able to help you as it will infringe on EA's copyright agreement.