Check this out for a super-easy hitch rack www.baxsie.com/quickclick

Mine clamps onto a 1 7/8 ball VERY securely and has stayed secure over bumpy dirt roads, interstate highways, etc. You can literally take it off and throw it in your trunk with one hand, or padlock it so it cannot be removed.
It holds 2 bikes, and is inexpensive.

BTW, a great way to keep bikes from scraping against one another on racks is to buy pieces of foam pipe insulation at a buck or two for a 3-4 foot piece and cut it into whatever length pieces you want. Slip it around chain stays, tubes, or where ever you want. They stay on in transit. I keep a length and a jack knife in my suv all the time.