Private lesson > Group lesson > Learning from a friend > Learning on your own.
> = "is better than"
This. Lessons from someone who knows how to board go a long way. Private lessons will do you the most good if you have limited time since the instructor can cater to your specific needs rather than just go through the normal routine for everyone. Plus if you pick it up quickly the rest of the lesson will consist of you shredding around with the instructor.
I took lessons when I learned in a group, but I was like 12 at the time and it was more fun with the other kids. Although I do remember near the end of the second day of my lessons I was much better than the rest of the kids and started to get bored.