Yes, just pull the fuse.
Or you can install a kill switch in place of the fuse, and run the wire into the interior. Then just turn it off. When ever you feel the need for it, just flip the switch and it will go up at 65 mph like it's supposed to.
Personally I don't think the spoiler is necessary until the audible warning sounds off at 95 mph. I think Chrysler just chose 65 MPH for it to go up simply because in the land where 65 MPH is the norm in most states, if it didn't go up until it was really needed, then nobody would ever get to see it.