You can use Disney Dollars at any Disney-owned venue at WDW, for food, merchandise, or even to pay off your room balance or enable charging priviledged on your key cards.
You can put down Disney Dollars at the begining of your
Disney cruise to pre-pay room charges, however, none of the shops aboard or on
Castaway Cay accept any form of payment other than room keys.
You can buy Disney Dollars from any
Disney Store in the US, or from WDW Mail Order - (407) 363-6200, or from Guest Relations at any of the WDW parks or resorts in the US and Puerto Rico.
Click the link in my signature for complete info on Disney Dollars.
Maryland_Mom, what part of Maryland are you in? I'm in Cockeysville, just north of Baltimore. I get my Disney Dollars at the Disney store in White Marsh Mall.