I've taken the exam in Herndon, but not Sunnyvale. The Herndon Juniper office and hotels are in close proximity to Dulles airport. I didn't even need a car. I wouldn't say its walkable, but everything is close. I stayed at a Hyatt House and had a hotel shuttle bring me to the Juniper office and the airport the following day. If you plan on using a hotel shuttle, just make sure to call and confirm that they are willing to drive you to the Juniper office. Also, when you arrive set up the shuttle reservation at least the night before your exam and leave your hotel early.. just in case you have to contend with people checking out and sharing a ride with you to the airport. You don't want to be late for your exam :).