Its easy and common. There are literally dozens of english language schools that cater to visitors. They have english programs as short as a month, so students can study for as long as they want while on vacation in Canada. Here is a partial list http
I taught at English Bay College, and my wife attended Global Village, both are in Vancouver.
Some of them are a bit expensive, but if you look around you can probably find something that is affordable, especially if you just do 3-6 months.