I can believe that the roots would not invade a dry foundation. But I also believe that a fig would invade wet spots like leaching fields, drainage pipes, etc. In an area with periodic heavy rainfall (not San Diego) the roots might follow the path of rainwater draining from the roof, gutters and downspouts.
My last house had a old stone foundation that seeped if there was too much rain. Roots then worked their way in as well, between the rocks. If the interior walls of your cinderblock foundation ever seems damp, I'd keep the figs away.