I used Photoshop to manipulate the picture a bit, and then added the text in white. Next I saved the photo at 300 dots per inch, sizing it to fill an area slightly over 4" x 6".
I pressed paper-backed fusible web to the back of a piece of fabric and fed the fabric through a color laser printer. When it came out I sprayed the print lightly with Krylon Fixatiff and allowed it to dry. I eventually added two more light coats of Fixatiff.
I prefer to use an inkjet printer for pictures that will be sewn into quilts, because the Fixatiff stiffens fabric quite a bit -- but that characteristic is perfect for postcards. Use either type of printer that's available.
I sandwiched fast2fuse between the fabric postcard's front and back and pressed as directed by the manufacturer. To finish up, I trimmed the fabric postcard to 4" x 6" and then added a fused binding.