Hi amanda,
I've used a mix of methods:
a) Roundup, let the weeds die, thick mulch and then lay black plastic, leave to rot for a year (good with fresh manure)
b) Thick mulch and lay black plastic, then plant through (if the mulch is OK to grow in e.g. compost, coffee grounds and fresh hops)
So far ::) the plants don't seem to have been bothered by competing weed roots and have done well.
If any weeds pop up through the planting holes, I pull them up. Not too many weeds are left after a year under black plastic, and any that survive have been weakened so are easy to pull out. But annual weed seeds seem tougher - when the area is dug or hoed afterwards, I always get a fine crop of annual weeds!
I do use roundup for areas of e.g. dock, thick cooch, bindweed and bramble. But only once.
Thanks for starting this thread, will try MT's method for some of my squash this year, sounds very simple and effective doesn't it? :)