"The downside: unless you're tooling around in a big West Coast or Northeast city -- particularly the usual suspects Seattle, San Francisco, L.A., Boston, New York, or D.C. -- you're less likely to have the hybrid option."  

One exception to this "usual suspects" list is Madison, WI, home of the fantastic car-sharing company Community Car (http://www.communitycar.com).  They have several hybrids in their fleet.