I will double/triple the suggestions to get a car hitch installed. Its not that hard. I have a corolla and all I did was look in the phone book under hitch. I think it cost $225 and took 1 hour. Then I got a 2 bike Thule hitch with a hitch lock from REI for $215 w/ tax. With my commute I have to drive part way so I keep the rack on my car all the time. It is much quicker and more secure than the strap on I use to have. Nothing is more of a time killer at 5 AM than dilly dallying around with straps in the dark.
One thing about Performance racks. I bought one of theirs first and as I was putting it together one of the supports that the bike rests on was loose were it attaches to the rest of the rack. It appeared to be from the round metal bar being out of tolarance. I took it back to the local store but I noticed it there the other day in the clearance section with another rack with the same problem. If anyone is close to Naperville, IL and is handy with this stuff I think it is $45 with an additional 30% off.