Just for another opinion, I've just finished Fundamentals 1 and 2, using my acoustic. Most of the teaching in those blocks are done on an electric, but everything is exactly the same. My sound is a little different, but the notes are exactly the same as long as you're in tune. I've started the Blues 1 section now and still, everything is the same. The fundamentals of the guitar are the same whether your using an electric, a steel acoustic or a classical with nylon strings. As near as I can tell, other than when you eventually get to the effects sections and some specific lessons in other styles it won't matter if you've got an acoustic. I haven't found it to be an issue with my learning at all.