I can't tell you whether to wear one or not - that's up to you. I've already said that my position is that I don't want the regret of not wearing one, should the unthinkable happen and I survive, but barely. So I wear a helmet.
In choosing a helmet it's important to know that ALL helmets in the USA must comply with the same safety standards. The only difference between a $20 and a $100 helmet is things like the air vent design, the harness materials, the aesthetics, etc. Functionally it is required by law to work the same.
So buy the cheapest helmet that you like.