That advice is not universally true, particularly in latin America.
In Costa Rica I couldn't find anyone who had ever heard of prepaid
service, so this wasn't an option.  In Mexico the two choices where
I usually visit, Telcel and MX Movistar, both charge prepaid accounts
3 pesos/minute ($0.27) for incoming and in-Mexico calls and 10 pesos/minute
($0.91) for calls to the US.  With the Cingular roaming rate being
$0.59/minute for all calls, whether you are better off with the
prepaid card service or not depends on your calling pattern (for
frequent travellers to Mexico who make heavy use of their phones,
nothing beats Verizon's North America's Choice plan if where you
visit has coverage).

Dennis Ferguson