They make plastics that are less sensitive to UV, should easily last a season.

A very thick covering of weed free hay (sheets of it-not loose) should do it just fine.
Plastic does nothing for your soil and do more harm than good by getting too hot and not letting in water.
You will never have no weeds in the garden but covering wtih a good mulch will go a long way and you can easily remove or work in before planting.

Thanks for the ideas. Haven't decided yet. Regarding plastic, what is better, clear or black? Regarding hay, I don't know where to get weed free hay, I don't want grass growing either. What do you think about using leaves?

why not lay a few sheets of plywood over it. they will hold up for a year, not much longer though.

Greenhouse grade plastic is UV stabilized and will last many years. If there are any commercial greenhouses in your area, you might be able to salvage some plastic when they replace it. It tends to crack along the edges where it is attached to the frame, and is most aged along the ridgeline. There should be enough good material left to cover your plot.

Although black plastic heats up more, it doesn't heat the soil as well as clear plastic. Even trying to solarize the soil with clear plastic only heats it a few inched down. This can kill annuals, some weed seeds, but may not kill deeper rooted perennials such as field bindweed.

A deep mulch will keep weeds from growing. This can kill established perennials. Many weed seeds will not germinate under the mulch and will be waiting for you to plant your garden the next year. The best way to get rid of the seeds is to solarize the soil, or encourage them to germinate then get rid of them by spraying, tilling or hoeing.

how about an annual cover crop?

I think a cover crop is a great idea. It'll replenish the soil, and then you can just till it in when you want to plant.

You could put down a pre-emergent like corn gluten meal, but I don't think that's a good idea because it leaves the soil open to things like erosion. Also, nature seems to abhor naked soil.

Why not plant winter rye or something like that and then just leave it?