If you do consider leaving it out bear in mind the following (taken from 'These Music Exams'
QUOTE
Ornaments are just another aspect of performance. If it is possible for them to be incorporated comfortably into the rhythm of the piece, they are always welcome as an additional aspect of the style. If playing the suggested ornament is going to upset the pulse, then it is much better to shorten the ornament into a turn or mordent, or to leave it out entirely to keep the structure of the piece intact. It is at Grade 6 that pieces really requiring ornamentation should only be chosen when the ornaments can be incorporated, even if in modified form. In the lower grades examiners are happy to accept performances without ornaments (although they will not be able to award the highest marks), providing that other musical aspects, such as phrasing and dynamics, have been given consideration.
As for the original question I agree with everyone else: on the beat, the purpose of the ornament is to accent the note it was on since harpsichords didn't have dynamics.