Airplane tickets

Hey guys,
I am flying out to São Paulo, Brazil next month. Last year, I flew with Continental but this year, they have the most expensive ticket prices! Anyone here have experience with these discount websites? (orbitz, bt-store...One has a 6 hour layover in toronto, canada..would they let me leave the airport and look around? ) Also, is it better to wait seven days prior to buy a ticket?
Thanks!
If I find interesting shaving stuff there, I will report back.

I've used expedia, travelocity, and whatever else google's found for me. All have pretty much the same prices, some have better terms than others.

Leaving the airport, that shouldn't be a problem.