I have a similar problem -- I live in NYC and have no car. As I understand it, my
secondary coverage of my VISA turns into primary coverage for collison because I
have no car insurance. That's the good news. But the bad news is that I don't have
the automatic carryover effect for third-party liability. Is there any credit card that
takes care of liability insurance? I'd check with my employer to see if your on-the-job
liability coverage would carry over to a rental.
Dave Feldman