Cheers Peter! (I'm probably too late with this response)...
You could create a web-based email account (ie. hotmail (
yahoo mail (mail.yahoo.com), etc., but you would, of course, need a way to access the internet while on travel. Unless you currently have an ISP who has local access numbers available in the USA, this might not be practical.
Another possibility might be to set up a trail account with something like AOL (America Online) or Compuserve since they have local dialup/connection numbers throughout the world. Some of my UK/French based users have subscriptions to AOL (US version, not UK or French version) and use these accounts when they're everywhere BUT in their own country. This may not be practical for you either since I think there is a surcharge when you use the service from anywhere except your home country??)
Then there is free email services like Juno.com, but you have to suffer through lots of advertising.
Realize, also, that no matter what you choose (if you choose) you have to advise people to whom you wish to communicate while abroad of your new email address (if different from the address you currently use at home or they will (obviously) try to communicate with you via your 'normal' email address (which wouldn't be available to you from your web-based account unless you selected on that allowed you the capability to use 'mail forwarding'.
The real key here is trying to find the easiest and cheapest connection to the internet, including a service that has a local access number in the city(s) to which you will be visiting (from where you need to access the account).
Regarding your question about calling cards... this wouldn't be necessary IF you chose a service provider that had a local telephone number from the location where you will be staying (here's where something like Juno.com/free email may be the way to go). Again, you need to find out whether the service you select DOES have a "local", non-toll, number available from the telephone line you will be losing. Note, also, that many local telephone companies charge a 'by the minute' or per call fee, even for local telephone numbers.
Safe Travels!