Problem:
To speed up english pages (especially backend, but also frontend) I suggest to change the icl string functions that will query the database for a string to return BEFORE the query (since english strings aren't translated anyway), if the current page is english (since default string language is english too).
Solution:
If English is the default language of the site, you can go to:
WPML > Theme and plugins localization > Localization options > Other options > check "Assume that the original language of all strings is English"
