the easy way to get back to San Javier is to join the E15 at Antas,,,, which is where you would have left on your inbound journey, but follow the signs to ALMERIA I know its the wrong motorway and you will be going the wrong way but trust me ,,,,,,,,,,,, follow ALMERIA and leave at the first exit and re-join the E15 following MURCIA you will then pick up the AP7 the "new " road to CARTAGENA..... its only 5 mins, ive done it and this is the best.
WETONE