The information on the Canadian immigration web page doesn't look too favourable. It doesn't simply refer to
convictions; it states "If you have
committed or been convicted of a criminal offence, you may not be allowed to enter Canada". (Since you must have admitted the offence in order to be cautioned, you've
committed an offence, even though you've not been
convicted of one).
If the Canadian authorities interpret that rule strictly, you won't be allowed into Canada until 5 years have lapsed from the date of the caution
and you've applied for, and been granted, 'rehabilitation'. The immigration website states "Applications for rehabilitation can take over a year to process, so make sure you plan for your visit far enough in advance".
You'll have to hope that the Canadian immigration authorities decide not to treat a caution in the same way as a conviction (although the website seems to suggest that they will). Otherwise you won't be granted a visa.
http://www.cic.gc.ca/english/visit/faq-inadmis sibility.asp
Chris