Is auoto focus important on a prime lens?

I want a 50 or 35 mm lens for my nikon d5000 but the cheap ones don't have auto focus. Honestly how important is auto focus on a prime lens?

The answer is always "it depends", but here are some thoughts:
The wide apertures give good opportunities for low light or fast action shots, and manual focus may be cumbersome in both situations. The D5000 viewfinder is also not as good as the D90 or D300, so manual focus through viewfinder will be difficult. I would suggest you get the Nikkor AF-S 35mm/1.8 lens, which is a very good low priced prime lens that will AF on the D5000.

Get a manual focus, it's faster. You can preset, you can zone focus, or you can guesstimate. Or you can stand there and wait for the stupid camera to make it's mind up.

If you are afraid to trust yourself on manual focus, read up on the electronic rangefinder function in your owners manual. (Page 61) The D5000 WILL tell you when it thinks you are in focus, even with a manual focus lens.

It's as important as you need it.

Well it depends on what you shoot and how you're used to shooting.

But generally a 50 or 35mm prime has enough depth of field in normal use that even if your manual focus ability isn't that great it should work comfortably. However with moving subjects it will definitely not be as easy as autofocus.

But hey, if you can't afford an autofocus lens but need the large aperture then buy the manual focus lens, If you can afford the autofocus lens, then buy it.