if you know the photoshop and if you want to learn autocad its very fast to learn...

IT DOESN'T MATTER U KNOW PHOTOSHOP OR NOT , U HAVE TO KNOW THAT PHOTOSHOP IS PHOTO EDITOR , FABRICATION , ILLUSTRATION , ECT..
BUT IF U WANT TO LEARN AUTOCAD IT DEPEND ON WHAT U WANT TO DO WITH IT , EVENTULALLY I CAN SAY U CAD LEARN EVERY THING IF U HAVE PASSION .
REGARDS

Photoshop is something much different than autocad ... But in a way or another both can complete each others to give a special work. Photoshop can help u in presenting ur work maps done using autocad in the best way.