If your American partner is criminally inadmissable, the chances of being deemed rehabilitated at the POE are slim to none from what I've been told. You're best off to send in the rehabilitation paperwork to be processed at the Canadian consulate closest to you. (used to be only Buffalo did them, but evidently, they couldn't handle the load!).
Current processing times for rehabilitation applications are 12 to 18 months unfortunately, so you'll be waiting a while for your partner to follow you, or you can stay in the US until it's completed.
See the Consulate website for info:
http://www.canadainternational.gc.ca/mi ... x?lang=engAlso, there are a very few at
http://roadtocanada.com forums that are waiting on this process currently (my husband included, but he hasn't sent the form yet), so if you're looking to gab with anyone familiar with the current process, someone there may be able to help you.