Take the A5 to Basel via Karlsruhe, exit at Rastatt before you reach Baden-Baden; Turn left in the direction of Kuppenheim. After the first set of traffic lights turn right, in the direction of Rauental and Kuppenheim. Drive through Rauental and Kuppenheim, and then follow the road to Baden-Baden, turning left following signs to Ebersteinburg.
Once in Ebersteinburg, follow the road to the top of the hill sign-posted towards the 'Burg Alteberstein'; immediately before you reach the final ascent to the Burg, Rainweg is on the left.
Take the A5 to Karlsruhe/Frankfurt via Freiburg and Offenburg, and exit at Baden-Baden and take the B500 towards the town. In Baden-Baden keep left in direction Stadtmitte (centre) and turn left to Ebersteinburg at the first set of traffic lights. Once in Ebersteinburg, follow directions as above.
You can travel by bus from Baden-Baden station to near the apartment in Eberstainburg. Take a bus to Baden-Baden Leopoldplatz, and change there continuing in direction Gernsbach (bus 214). This bus will take you to Ebersteinburg. Alternatively, a taxi from the station will cost you approx. 20 EUR.
Baden-Baden has its own airport west of the town which is served by a number of budget airlines. Car hire is available at the airport. Alternatively, you can easily take a bus to the centre and then follow directions as above; or you can take a taxi which will take you straight to the apartment.