It justdepends. Some people do better with lessons. Myself, I felt that 30 minutes per week with the bullshit material the guys at House of Music taught me wasn't worth it. I had a cool teacher for a while, Tony Dyer (of the bands F5 and State of Mind, voted in the Illinois Times as best guitarist in central Illinois) but after he quit, so did I.
I progressed a lot faster on my own. With the wealth of information on the web, you can do pretty well on your own if you're self motivated.
I haven't played regularly in 2 years, 1 of which I didn't have my guitar around, but I'm about to get a new amp (old one was stolen) and pick it back up.
My life's goals were always as follows:
1. Move to southern California/LA area.
2. Hook up with a gorgeous woman.
3. Join/form a band and become famous.
I've already accomplished 1 and 2, and I'm ready to go for #3 (although I have been in bands before, in Illinois).
EDIT: In regards to what smalien said, it really is a good idea to learn to read music. But for now, you can easily learn some simple songs via tablature, which just tells you which frets and strings to place your fingers on.