The chip/pin issue is becoming more common. However, all merchants are required to accept non chip/pin cards; unfortunately, not all clerks know how to do so. Sometimes there is a "no pin" or "signature button"; sometimes pressing cancel or waiting for it to timeout when "enter pin" is displayed will have the transaction go through for a signature purchase.

Here is some info from the Visa website:
http://www.usa.visa.com/personal/using_visa/european_travel_tips.html?it=c|/personal/using_visa/travel_with_visa.html|European%20Travel%20Tips%20