on my opinion, if you've got some computer skills, such as can operate win98 or winnt.it is not a difficult thing for an industrial electrician to master the PLC.
if you want to learn PLC, I think that to learn AB's slc-500 is a good choice.since there are so many kinds of PLC, we don't need to learn all of them, we just need to learn one of them, once you know the theory of it, all of others are the same.
it is appreciated that anyone have other good suggestion for learning PLC