I usually park at Rees, directly south of the dome, between Lakeshore and Queens Quay. But this is also the last weekend, and the Yankees are in, so you never know.
I tried the Go Train once. Total waste of time, imo. Coming from London, I could drive to the stadium, leaving shortly before 11, and be in my seat shortly after 1, and this was back in the 50,000 per game days. Taking the Go, I had to be in Oakville for the 11am train, as the noon didn't really leave enough time, with the walk back from Union. I'm not sure what the schedules and fares are like now, but I'd just as soon pay event parking prices and free up a couple hours of time.