I tend improvise mostly from ear, meaning I don't really know what scales I'm working off of (not that I'm proud of it)but if you can play the melody line and then improvise around that it gives you a base to return to and I think is pleasurable for the listener. Many jazz players I know use that approach. But definetly, the more fluent you are with scales and being able to play them anywhere on the neck will be very valuable to you. Good Luck. Tom