Hi there,
First of all, welcome to the forum, and welcome to Ontario.
There are lots of good deer hunting opportunities in Eastern Ontario. When you first get here you will want to sort out your license requirements. Visit the Ministry of Natural Resources Site for information on Hunting.
http://www.mnr.gov.on.ca/en/STEL02_168294.html
I don't hunt near Cornwall myself, but there is a good mix of agriculture and forest around there. You should be able to find some public lands to hunt, but your best option will be to knock on some doors and get permission on private lands. Public lands will include county forest and Conservation Authority properties. A short drive north, you will find find lots of crown land, open to residents of Ontario. If you have any specific question, please feel free to send me a private message.
Cheers,
Tenpoint
The weak can never forgive. Forgiveness is the attribute of the strong.
Mahatma Gandhi (1869 - 1948)