If they jump away like a flea when you pass your hand close to them, they are flea beetles, your critters may be larger than flea beetles. Flea beetles can do a number to cole crops.

Try saying "Little Black Broccoli Bugs" three times in rapid succession.

Al

Do they appear to be harming those plants in any way?
About the only thing that comes to mind they might be in the pest catagory is Darkling Beetles, however they may well be predators also.

Al, will that help, or just be fun for onlookers to watch?

Michael, no, they don't jump like fleas. I can squash them pretty easily with a finger (and end up with brown goo smears everywhere), but that's not really my preferred method of control if it doesn't have to be. There's just too many of them...

Kimmsr, the plants have holes eaten in the leaves, and some of the leaves are nearly nibbled completely off, but that may have been from the worms, not the black bugs. So I really have no idea if they're beneficial bugs or not, but I'm guessing not...

This doesn't exactly match your description, but I had problems with black aphids on my broccoli this past year. There were zillions of them, in thick clumps, and they didn't rinse off with a hose or in the kitchen. Ew.

Some beetles eat aphids, you should find out what they are before you kill them, they may be trying to help you

Capture some in a ziplock bag & take them to your county extension service for ID. Then you will know what to do about them.