Here is what you got to do.
Edit your /etc/ttys file.
There you see your ttyE0 standing on secure and the others off secure.
Put ttyE1-E3 on secure and there you go.
Btw, alt-F2 wont work. Use always ALT-CTRL-F2 or F3 and then it works.
Btw, first make the changes active after you editted the file.
Sincerely,

Reinoud.