[QUOTE=Tempus Fugit]What is the best calling card to use to call from Mexico to the USA?QUOTE]

If you have a good connection from a hotel or internet cafe, use Skype and SkypeOut. http://www.skype.com/
Skype is free, computer to computer phoning; SkypeOut is to call from your computer to a land line or cell phone, it's 2.3 cents US per minute. If you connection is slower than a slow DSL it can be a bit tinny, choppy; I use it on a 144 k connection and it's generally OK calling to land line phones and very good calling to other Skype computers. I don't know if it will be workable on a 56K dialup.