I still say - hop the Greyhound and forget the already-booked tour buses. You'll have more fun.
Schedule
http://greyhound.ca/scripts/en/TicketCenter/Step3.asp

Fares
http://greyhound.ca/scripts/en/TicketCenter/Step4.asp

I chose Tuesday July 15 as a departure/return date. There are discounts for students and also for "non-refundable" fares, and you get a buck or two off if you reserve at least a day ahead of time.

Cheers!