Larry (and others) made some good points about teachers and I would echo his suggestion about group classes. I started acoustic guitar this way and having other students in the class was great. I am still good friends with the teacher and we jam, etc. whenever we can.
The great thing about classes and a teacher I think is accountability. If you're paying and have an appointment or class you need to be at, you go prepared. No goofing off and not getting your homework done.
