Your information is incorrect.

Campsites will usually open the weekend before the May long weekend (Victoria Day weekend). The May long weekend usually falls somewhere between May 19th and 25th, depending on the year. Off hand, I have no idea when it is in 2006. But the campsites usually open the weekend before that to make sure everything is set up and ready to go for the May long weekend.

A word of caution: the May long weekend is a HUGE camping weekend in Canada. If you want a site on any night of that weekend, you'll need to book ahead.

You will not likely find cheap hotels through there, especially once you get closer to Jasper. "Cheap" up there is usually over $100, and once you pass the May long weekend, it could double in price. Also, if you are thinking of hostels, again, after the May long weekend, you'll need to book ahead in the National Park.

Incidentally, the road from Vancouver out to Mission, and a bit beyond Mission is quite busy with narrow shoulders. You might consider heading south once you get into Vancouver to White Rock, and then on to 0 Avenue. That one runs right along the US/Canadian border and is fairly quiet. When 0 Avenue ends at Townline Rd, you could head north into Abbotsford, and across the river to Mission and carry on from there ... or you could head north on Townline to Huntingdon Rd, then east on Huntingdon as far as it goes, then north on Powerhouse Rd, then east on Wells Line, then north on the Inter-provincial Highway, then east on Campbell Rd, then north-east on Towne Rd, then north on Boundary Rd ... and basically follow the mountain, north and east to Chilliwack.