A quick follow up, in case anybody is following this thread.
The first time you fire up a new hp you are going to need a viable Internet connection. Every one that I have seen needs a firmware update before it will work with AirPrint. So don't just buy the printer and go straight to grandma's house. Get it updated and working first, then go.
Second item. I tested it on an I phone 4 hotspot, and it worked fine. I believe it should also work on a droid, windows phone, or a mifi device, but have not tried. It would be interesting to see if it does, and if any of you have a pad, an AirPrint printer, and one of those devices, give it a try and report back.