Hi Emmagail, check out this site, http://www.cic.gc.ca/english/visit/faq-inadmissibility.asp
This should give you the ins and outs of rehabilitation.
Another site, will give you what is deemed criminal in better length. As you can see a DUI is considered criminal and it would be in your best interest to leave the country before applying or you may run into trouble for being here having not been rehabilitated and were lucky enough to slip through the system. Really not trying to make this difficult for you, just looking out for you.
Are you inadmissible to Canada?
Please read the following information carefully:
In general, people are considered to be criminally inadmissible to Canada if they were convicted of an offence in Canada or were convicted of an offence outside of Canada that is considered a crime in Canada. In order to enter Canada, these people must obtain Approval of Rehabilitation or a Temporary Resident Permit at a Canadian Consulate or Embassy.
Offences involving operation of a motor vehicle while impaired by alcohol or drugs will, with very rare exceptions, render persons criminally inadmissible to Canada and therefore in need of Approval of Rehabilitation or a Temporary Resident Permit to enter Canada for any purpose and any length of time.
Approval of Rehabilitation
Approval of Rehabilitation may be granted if you can show that you have a stable lifestyle and that it is unlikely that you will be involved in any further criminal activity. You may apply for rehabilitation if five years have passed since the end of your sentence. Periods of probation are considered to be part of the sentence as are payment of fines and restitution of a driver's licence.
Approval of rehabilitation permanently overcomes inadmissibility arising from the offence declared.
Temporary Resident Permit
If you are inadmissible to Canada for criminal, medical or other reasons and there are compelling and urgent reasons to allow you to enter or remain in Canada, you may apply for a Temporary Resident Permit.
Offences involving operation of a motor vehicle while impaired by alcohol or drugs will, with very rare exceptions, render persons criminally inadmissible to Canada - and therefore in need of Approval of Rehabilitation or a Temporary Resident Permit to enter Canada for any purpose and any length of time.
A Temporary Resident Permit temporarily overcomes inadmissibility.
Authority to Return to Canada
Use this application if you are seeking authority to re-enter Canada prior to the expiry of an Exclusion Order or you are seeking authority to return to Canada because you are the subject of a Deportation Order.
Note: If you have urgent and compelling reasons for entry to Canada within the next 6 months and are eligible to apply for Approval of Rehabilitation (i.e. beyond the 5 year prohibition), we encourage you to submit your Approval of Rehabilitation and Temporary Resident Permit applications at the same time.