Flights from Canada

Hi there. We are trying to book flights from Calgary to Puerto Vallarta for January 2003. Any tips at all would be appreciated. Good to book now at $850. or wait until later? Any suggested airlines to call direct or better to go through a travel agent?
Thanks

Barb

If I could find a flight under $700. taxes in I would grab it. Right now they are around $850.00. Kind of a lot!