Too late. If you trim the forsythia now, you will cut off this years flowers. Forsythia flowers form on last summers growth. Wait until the flowers are gone next month and then prune.

I agree that they should be left until bloom is spent, but my personal preference is either cut them to the ground and let them grow and fill in for a few years or thin them. They look terrible sheared into buns.

I agree with bogturtle about sheared forsythia; their lovely fountain-like shape should be maintained if at all possible. To bring them down to size if they are overgrown, try renewal pruning: Remove up to one third of the canes down to the ground, focusing on the oldest canes and any that are diseased, damaged or growing in an awkward direction. This will promote new basal growth. You'll be surprised how much more "civilized" they will appear afterwards, and yet will still retain their natural shape.

I want to move mine in a week. I am planning on putting something different in their area.