Every two years when we go to the US, the mobile phone landscape has changed dramatically. That means that in order to get ourselves working phones for the month or so we're there, we have to re-investigate everything and figure out the best option every time.
I don't remember what we've done every visit, but I remember that four years ago, the best option was to buy a cheap phone with a SIM included and use the associated pre-paid plan (other options were tied to long-term contracts). Two years ago, we got SIMs to put in our existing phones and used some kind of pre-paid cards to charge them with units for texts, voice, or data - no contract needed.
This time around, the field seems even more open. It looks like we should have no problem buying a US SIM to put in our own phones. However, I am dismayed at the cost. From my research (and please tell me if you know better!), it looks like we'll have to pay a minimum of around 40USD/month to get a pre-paid plan approximating what we have in Finland (unlimited text/voice/data 3G or 4G for about €20-€25-month). Even limiting certain aspects only takes it down to 30USD or so.
In Finland, there is also the option to buy a SIM card for 5 euros and then just pay only for what texts or calls you send/make. If you want data, you can pay for that bit by bit or max out and just pay a euro per day. I'd be interested in something like this for the US, if the price was right. I'm also wondering whether we could get away with no data (only wi-fi), or ONLY data.
One last note - arranging to turn off our mobile phone plan for a month while we're gone brings back memories of trying to do the same thing ten years ago when we'd go to Jordan for the summers. This was in the days of stranglehold mobile phone contracts in the US. T-Mobile would always ask us where we were going and then suggest we just use their roaming plans there (at something like 8 bucks per minute, ha). When we declined that, they asked for proof of residence in Jordan. Without it, they wouldn't put our contract on hold. Ridiculous. I'm glad to see the US moving away from those horrible contracts.