I've noticed the sparcity of SoDak posts myself. I live near Rapid City, open carryingwhileregularly hiking in the surrounding Black Hills & occasionally in town. However, I seldom see other private citizens OC. But, rest assured that Rapid City is a gun friendly town in a gun friendly state.
If you go to the website Handgunlaw.us , on the left hand side of the home page you'll find info on places off limits. Basically: K-12 schools, Court Houses, Bars that get more than 51% or more of their revenue from alcohol, Mount Rushmore Natl. Mem. & Wind Cave Natl. Park, etc.
You're good to go in resturants, State Parks & Campgrounds. As usual verifyallof the abovefor yourself.
Enjoy your stay.