Do I really need lesson? That's what most beginner snowboarders usually ask.
The answer is YES!
Sure it's costly to rent all the gear and then add a lesson on top of it, but isn't that cost worth the risk of minimizing injuries on the mountain? Taking lessons will also get you on the fast track to learning the basics and help to avoid picking up any bad habits.
So now the question is... private or group lesson? If you have the funds, go private. Private lessons will offer you personal attention and the time to learn at your own pace. If private is out of the question, try to find a group class that is not too large. With a huge group, the instructor may not have the patience to slow things down if you're having a hard time keeping up.
If you're lucky enough to have a buddy who has mastered the basics of snowboarding, hit him up! The problem of course is if you're friend is like most snowboarders, he's probably more interesting in conquering the mountain than giving away free lessons.