Thanks for making phone calls for me! Thanks to Pat, I found out that the AT&T store in the Galleria Mall in Fort Lauderdale does stock the phone I need. I didn't want to take the trouble to travel up there by taxi or bus only to find out I needed to order the phone through their website; I could do that today, but would have to deal with delivery issues.
As for the store at Crown Bay, no one seems able to get them to answer their phone. They're supposed to be open Sunday from noon to 5pm...that's an easy first step to walk over there. Somehow I'm not hopeful they're going to 1.) still be there; 2.) actually be open on Sunday; or 3.) have the phone in stock. It's the islands, mon. It's good to have Fort Lauderdale as a back up.
Thanks again for all your help!