Ray, (Turbo) has far more experience with hydroseeding than I, but here goes my two cents, aside from that Vancouver is a great place to visit. My only concern is like Hydro's, keeping the seed in place. Are we talking predominately flat ground with gentle slopes only?
If so, hydroseeding now and keeping the seed in place should not be a problem. If you have more extreme slope I would have some concern. I would favor a wood blend, partially because you can go at a higher rate than paper mulch, go with a high rate of tack.
We have gone with a BFM mulch on sloped areas for extra 'insurance' and that has worked very well. Snow cover and frozen ground is actually a good thing as the seed and mulch cant move. Heavy rain is always going to move the seed and some mulch but rarely enough to be a factor except if you have heavy enough rain to cause some gullys.