NickB- as David D has mentioned, you don't have to pay the departure tax in UIO if you're staying less than 24 hours. You should stop at the departure tax booth to get your exemption (in form of a receipt).

As far as UIO hotel, my recommendation is the Four Points Sheraton. They have a complimentary shuttle. You can call the hotel ahead of time to make arrangements. They will be there waiting for you as you exit the airport. The staff is very helpful and attentive.

If you have time, read my short UIO trip report at http://www.flyertalk.com/forum/Forum81/HTML/000889.html

Best of luck on your trip!