I'm 6'1 and ride a 17.5". The real thing that you should be concerned with though is your inseam from what I've heard. For a freeride frame though, usually riders like them to be a little small so that they can maneuver it better and they have a little more clearance.
If it doesn't end up fitting then definately ask for a refund. It takes some of the fun out of riding to have to ride a bike that doesn't fit right.