Kelly-Rudbeckia hirta is the annual kind you're looking at and it does spread around promiscuously, for sure. If you have an interesting form, like Prairie sun or Summer sun, just let them go and remove as many as you can to control them. But, if you just let them go you will have one giant garden of yellow.

Rudbeckia 'Goldsturm' travels by underground runners as well as reseeding itself. It's a chore keeping it under control. I dug up tons of plants this spring and gave them away. Now there are more than I had before. Arghhh! They sure are beautiful this time of year though.

The simplest way to avoid plants re-seeding is to deadhead the flower before it sets and disperses seed.

Ours seem to stay put pretty well, but that may be because we have them hemmed in by some pretty deep garden-edging stuff. Still-- they're lovely and they are pretty pest-free. I'd just let 'em spread!