I live in "central" BC, Canada and wouldn't mind trying to find some mushrooms.

Shroomery listed these mush as growing in BC:

Conocybe cyanopus
Gymnopilus luteofolius
Panaeolus papilionaceus var. papilionaceus
Panaeolus subbalteatus
Psilocybe baeocystis
Psilocybe cyanofibrillosa
Psilocybe cyanescens
Psilocybe fimetaria
Psilocybe pelliculosa
Psilocybe semilanceata
Psilocybe sierrae
Psilocybe silvatica
Psilocybe strictipes
Psilocybe stuntzii
Psilocybe subfimetaria

but which would I be most likely to find this time of year, and where? Mountains, valleys, lawns?

having just returned from a successful three-day hunting trip in southwestern australia, I can tell you that pine forests are an excellent place, the older plantations with shit tonnes of big trees and needles on the ground to at least three inches of depth. any fallen limbs should be moist or rotting to the point where even a large stump will crumble if you step on it, and if possible there should be a river in the area. This, we have found, provides dozens and doozens of shrooms of many different varieties, averaging 3-4 psychoactives per square metre, mostly ps. subeu, blue meanies and straight up subcubs.

If you don't already know this, you don't know enough to pick mushrooms Not trying to talk shit, but it can really be that dangerous.

http://www.shroomery.org/6235/Mushroom-Hunting-FAQ

http://www.shroomery.org/6235/Mushroom-Hunting-FAQ

Good advice.