It's pretty flexible; each day I use roaming data there is a per-day charge and a per-day data limit, which is good for very light usage. If I hit the limit, there's another automatic charge which gives me a lot more data which I then have a month to use up (if I've understood the website correctly). Sort of self-tiering access. I actually intend to do this if I can't find enough Wifi.

I was mainly interested in whether I could use a local SIM to acquire a US phone number but it sounds difficult. I need to organise a transit card when I land anyway so I'll also ask there about a pre-paid SIM card.

Wade.