Hmm that's strange but when you start up and you're on login screen, in bottom right corner I think there will be an image of keyboard or maybe access icon that you can click and it'll give you the option to open touch keyboard. You click on it, and when it opens, in bottom right corner it will have one key that will show what language is currently selected. If it says anything other than ENG, click on it and select english instead.
As to why it keeps reverting, again make sure you go into your settings, and set english as default once you're able to get in.