AT&T sells a plan with 5GB/month for $50/month[1] (pay-ahead, not prepay). It is a monthly subscription with no commitment - cancel it at any time. I walked into a AT&T store and the lady behind the counter gave me a free SIM (list price $5.95). I bought the $15/month for 250MB data plan since I was just experimenting.
I found out that AT&T has annoying restrictions based on the IMEI number - for a IMEI that maps to a computer, they will only offer you the $50/month plan. For a IMEI that maps to a tablet, they will allow you to to buy the $15/month plan. FWIIW, they require you to enter a IMEA number, not the number of the device you are using the SIM in. ;-)
I am currently running my phone on a T-Mobile on a $30/month pre-paid plan[2] with unlimited (for some definition of "unlimited") data and 100 minutes of talk. Unfortunately, they have poor coverage in about half the area I frequent... I end up roaming on AT&T and don't get data coverage there.
Both those options are essentially the same as your Singapore plan.
Jesus, a 2-year commitment to a shitty voice plan just to get a 3G data sim?
I'm visiting New Zealand now. The first thing I did when I got off the plane was purchase a 3G prepaid (2GB) USB dongle for $70, and I can top it up if I need to and move the sim card to a phone if I want to. I didn't have to sign or agree to purchase anything extra.
I can do this in Australia, too. What the hell, USA?
Note that the plan you really want is the "Tablets and Gaming Devices". The "Computers, Netbooks, Aircards, Others" plan is a rip-off except for the $50/month 5GB plan, which is the same as the "Tablet" plan. On the "Computers" lower data rate plans, it is $15 per day, $30 per week. Data is data, so they are just ripping you off.
AT&T DataConnect Pass plans
* No Long-Term Contract
* Plans are active for 30 days or until depleted.
* Plans automatically renew every 30 days for domestic data plans, unless you cancel.
I found out that AT&T has annoying restrictions based on the IMEI number - for a IMEI that maps to a computer, they will only offer you the $50/month plan. For a IMEI that maps to a tablet, they will allow you to to buy the $15/month plan. FWIIW, they require you to enter a IMEA number, not the number of the device you are using the SIM in. ;-)
I am currently running my phone on a T-Mobile on a $30/month pre-paid plan[2] with unlimited (for some definition of "unlimited") data and 100 minutes of talk. Unfortunately, they have poor coverage in about half the area I frequent... I end up roaming on AT&T and don't get data coverage there.
Both those options are essentially the same as your Singapore plan.
[1] http://www.att.com/shop/wireless/data-plans.html
[2] http://prepaid-phones.t-mobile.com/monthly-4g-plans