other options....
As a person who avoids driving at almost all costs (haven't owned a car in years), I have to caution you about public transit from DTW. I've taken that bus to downtown, and promptly arranged a taxi for my return to the airport.
It's not PDX. The buses in Detroit run infrequently and slowly.
Ironically, there is a 15 dollar shuttle bus to Ann Arbor or East Lansing, but for Detroit proper, the Taxis and limos seem to have a monopoly and charge 45.