I rented a PT Cruiser from Enterprise for $70.59 after taxes, fees (including the under-25 fee). This did not include gas, which cost another $8 or so (you should fill up at the Mobil near the Enterprise station, since they charge much higher per gallon to fill-up).
I would rent a car because it is about the same as calling a taxi, but you don't have to be at the mercy of the taxi to get around places. For example, you may want to leave your hotel to the local Walgreens or WhiteCastle, or you may want to check out the neighboring region or Chicago in your spare time. Also, there was a fellow interviewee who waited in front of the med school for over one hour waiting for her taxi, and she would have missed her flight, had I not given her a ride to the airport.
Caution: 294N automatically turns into 94East. I also recommend resetting the trip meter when you leave the rental station, so you don't go for hours having passed an inconspicuous little sign that says "Buckley Rd." Also, they have toll roads, about $.80, so bring change, especially on your way back. Further, get specific directions to the rental station. Chicago roads are not as clearly marked as they are in Los Angeles, and can get complicated near the airport.
I stayed at the Ramada Inn Waukegan. Your room will be quiet, comfortable, clean and have free WiFi, in case you bring your laptop. They give you a voucher for a free continental breakfast the next morning (but I didn't use because I overslept). If you call to reserve a room, mention you are coming in for an interview, and they will charge you a lower rate of $70.75.
Hope this helps, and good luck!
Ramada Inn Waukegan
http://www.ramadainnwaukegan.com/
847-244-2400
Enterprise Rent-A-Car
http://www.enterprise.com/car_rental/home.do
(847) 928-3320