Brian,
Do not skimp on a helmet. It protects your brain housing group; a non replace-able item If you're not sure, borrow a quality lid for your test from a friend. Then, if you decide riding is right for you, invest in something from Arai, Shoei, Bell, or Simpson.
My personal preference is a full face lid. It my more conservative (safer) side. James is right, you want SNELL. Not just DOT or ANSI.
Mark-who-has-been-down-twice-since-1985-and-was-grateful-for-a-good-helmet-both-times.
