GravityForms received a feature request two years ago to add the ability to change the description location on the forms from below the input boxes. Instead of putting it AFTER the field, the request was to place the box description above them.
Last year, they listed it as a future feature, but as of version 1.6.9, (today) this feature is still not available. They do still have this on their list for a future release, but in the mean time, this can be accomplished by adding a piece of code to your theme’s header.php.
To move the description from this location: