Arriving into LAX in a couple of days, and was planning to get organised with a SIM card for my week long stay either at the ATT or the TMobile stores near LAX.

I'll be travelling with an iPhone 5 (A1429 which supports UMTS/HSPA+/DC-HSDPA (850, 900, 1900, 2100 MHz); GSM/EDGE (850, 900, 1800, 1900 MHz); LTE (Bands 1, 3, 5))

I know ATT 3G network uses 850 MHz, and have read about TMobile rolling out a 1900 MHz network (Las Vegas and Los Angeles both appear in the list of cities where this network is "live"). If I can get 1900MHz 3G coverage in those two cities, I'm happy to go with a TMo $3/day prepaid option that gives me 200MB of "upto" 4G data each day.

Alternately, I'm happy to just stick to ATT that I have used before. Last time around, I got set up with a microsim from the ATT Store + the $25 plan (250 minutes, unlimited texts) + $25 data pack (1GB smartphone data). I vaguely recall ATT charging me $20 or so for the actual SIM (which I assumed would be available for free).

Anyone care to comment? And shed some light on whether ATT makes available nanosims for prepaid use, and at what cost?