You said your referral code is $20 right. I live in Canada so i wonder if it still $20 here. I never use Uber so i don't know if you can share the ride with your friend or not (we live together)?
I need Uber for college and will buy it daily.
The least you could get for a free ride is usually $10 in U.S, Canada, Aussie. Even if it is, you still save. Don't worry.