I live in zone 7 (I think) - west coast of Canada (Vancouver
specifically) and I have been having an awful time getting cucumbers
to grow.

Each year I get the sturdy little plants from the local garden shop,
make sure they are properly hardened off and growing well then plant
them into the garden. Once in the garden they grow very poorly and
seem to have an awful time on sunny days.
Days that are mainly sunny the plants wilt really badly even when the
soil is moist and don't recover until well into the evening. I've
tried planting them in a shadier spot but then I have to deal with
mildew on the leaves.

Does anyone have any advice? I'm sure that the market gardeners in our
area grow cukes in the full sun without any problem so what is the
matter with mine?