Gardening

but they won't allow bees in, although unless you're saving seed that's not really an issue. Although the one you linked is probably too widely spaced to work. You need something more like this:
http://www.burpee.com/Gardening-supplies/garden-growers/floating-row-cover-prod001213.html?cid=PPC

It doesn't take much time to inspect plants and remove them though. I grow a lot of broccoli, and once a week I'll inspect the plants (20+). It takes about 15 minutes.

Carefully turn over each leaf and remove the pin-shaped eggs from the underside, look for damage on the leaves and look for a worm. They blend in really well, so sometimes you have to stare for a few seconds before they pop out. This 15 minute once-a-week routine removing the eggs before they hatch and any hatched worms easily keeps the damage at a minimum.

Spending the time inspecting the plants also alerts you to aphids/other problems that may need addressing.