Yes we call a function isWhitelisted before doing any blocks and if the IP matches, it returns immediately. So it's safe. However please ensure you're running WF 4.0.3 because 4.0.2 which was only out for a few hours until we fixed it contains a subtle bug which may interfere with this.
Regards,
Mark
PS: If you found this helpful, please rate Wordfence 5 stars.
http://wordpress.org/plugins/wordfence/