Prepaid SIM card
I have a European mobile phone. I'd like to have a prepaid SIM card with local number for guests.
If your phone is unlocked and works on GSM networks go to Radio Shack or the AT&T store and pick up a prepaid phone with a SIM card. You can either use the inexpensive phone that comes wi a prepaid plan or take the SIM card and put it in your unlocked phones.
No vending machines selling SIM cards like you see in rail stations and airports in Europe.
AT&T goPhone SIM cards will be locked to the phone they're purchased with for the first 6 months, so the SIM will crash if you try to put it in your existing phone. Go to AT&T and buy a SIM card by itself. Don't try putting one that came packaged with a GoPhone into a phone you already have--it doesn't work.
Radio Shack sells TracFone. Maybe that's the answer.
Minutes cost more on TracFone than they do on AT&T. The new basic by-the-minute plan through AT&T is 10cents per minute, while a $20 card for TracFone, last time I checked, only came with 60 minutes. Your other option is AirVoice next to Plaza.