I'd like to buy a digital piano for under $500. I found the Privia PX-130 but I was wondering if there is anything out there that is better for the same price.
Someone once told me that a Yamaha (of the same price) is better than a Casio Privia.
The PX130 is about lowest priced digital piano you will find. But I noticed the price was lower a couple days ago at my Local Guitar Center. (maybe it was $470) Casio does make a CDP100 that is slightly less expensive and Korg has announced an SP170 in your price range too but it has yet to hit the stores so no one knows yet if it is good or not.
Yes Yamaha might be better than Casio as you move up to higher price points Certainly if you were looking for a $1,300 piano I'd suggest a Yamaha over the Casio.
About the book to learn with. Yes the "Alfred all in one" book is good. But get the version of the book with the DVD. You will only need to watch the first part of the DVD, most is just some guy reading the book out loud but the beginning shows you the correct posture and finger position. It's also good to have the CD so you can hear what the piece sounds like before you play so you can have a goal.
People argue over which book is best. But in the end they all cover the same material and the difference are minor. So choose based on secondary considerations like the huge on-line support group here.
Of course having a real teacher is best, by far.