Pressure washing could damage the wood depending on how weathered it is. Is there Moss or algae on it?

I would not paint a fence. I stained mine.

I don't have a close picture, but you can see it pretty well here:

I don't think there's any algae or moss; it all appears to be dry. I've had to replace several pickets over the years, though, so some of them are darker, almost black (which I guess implies algae; my spare pickets are in a shaded, woody area behind a shed).

I would consider stain, but it would be pretty expensive for the coverage I have, where I have 15-20 gallons of dark paint that matches my trim just sitting around. If I have to get it pressure washed and then buy a lot of stain then I'll probably never get around to it... but if I can get away with painting it as-is then I might get it done over this weekend :-/

That's a good answer.

The paint might peel eventually. But if you are after an easy fix for a while, who cares?

It looks a little rough in spots. If the wood is soft and porous, maybe just brush it down with a stiff bristled broom. Otherwise try a section and see. For the black streaks you could try bleach.

Post a photo when you finish!

Will do! Thanks for the input :-)