You will be parking at the OUTPOST DEPOT... remember that.
To get to the Hoop Dee Doo, you will want to board any bus that says "SETTLEMENT" on it. Doesn't matter if its the Yellow, Purple, or Orange...
To get back to your car, just board any bus that says "OUTPOST" on it... once again, doesn't matter which color. Each color takes a different route, but they all end up at the same place, and take about the same amount of time, give or take 60 seconds.
Make sure to read the signs, and look for those two words... The bus ride itself is typically 2-5 minutes, tops.