When you say, "It is highly recommended that you go the other direction, because of the prevailing winds" what are you basing that on?
If it is just the prevailing westerlies, I would question the advice. Surface winds don't generally follow that pattern at all. If you have specific advice based on that particular route and actual surface wind conditions that would trump my comments.
I am convinced that for a coast to coast trip on the TA for example the places where the wind matters most (Kansas and Eastern Colorado) are likely to have winds out of the SE in mid Summer. Places like Wyoming and Montana are tougher to call. In Canada I have no idea.
Bottom line... I really don't know what is better for this route, but do know that it is probably not wise to count on the prevailing westerlies as a general rule.
Edit: Check this map out
This message was edited by staehpj1 on 10-10-08 @ 8:27 AM