Still way too much going on for a billboard. It's gotta be short and sweet. One quick message. You only have a moment to communicate.
If you don't mind me asking, why are you considering billboard advertising? I really feel that billboards are only effective for larger companies who can afford to use billboards as a backup to a larger marketing plan. Billboards are not good brochures. They are great for reinforcing a brand or product... but not much more than that.
Depending on the billboard you are considering renting space on, I feel your money would likely be much better spent renting a giant box truck for a few months, wrapping that with the design on your billboard mockup and driving it around town all day, every day.
Andrew