You'll find learning a manual after driving an automatic quite difficult, it'll be a totally different way of driving. Once you've learnt auto you'll probably stick to it.
If you want to drive auto only there's nothing too much wrong with that in itself. You're limited in what you can drive but a lot of cars are auto now and modern auto boxes are quite good. Just don't become one of those people who are so disinterested in driving that they get preoccupied with other things, because they are the worst kind of people.
With that being said, I don't think learning to drive an auto will save you much time. A couple of weeks maybe. Clutch control just takes a few hours practice, where as observations and road reading are purely down to experience and aren't improved by only having two pedals to think about. A number of 'experienced' drivers get scared of motorways even though you can often just keep it in top gear, simply because you have to be so aware of what's going on around you.