Thanks, all.
I found this site as a source for a 3G data card:
China 3G Mobile Broadband / China 3G SIM card, for rental, hire and sale
The web site is very professional in English. They responded fairly quickly to questions I had. Cost would be $69 for 1.5G, $89 for 3G. They deliver SIM to your hotel and will pick it up if you leave it in a hotel in a different city when you leave. (If you don't return the SIM they charge you $50.) For $10 more, they will give you a VPN to use to access banned services.
We rarely would need to make outgoing calls. I hope Piranha works for incoming. They access both of the main networks in China. I am also hoping most of the hotels we will be at have usable wifi. I had no trouble in Vietnam a year ago using the UMA (wifi) calling feature on my T-Mobile Blackberry. At 1mb/min. for calling over wifi, using the data card would be about 7 cents/min. [I think I did the math right
]
...mike
Make use of T-M's UMA/wifi free calling from any place in the world with access to wifi. I use an LG G6, wife an S7)
A/o Oct 20, 2013 no need for intl prepaid as T-Mobile U.S. includes voice roaming at 20¢/min (in and out)., unlimited text (in and out), and unlimited data in 140+ countries.
My Plan -[6 lines] U.S. T-Mobile unlimited minutes (incoming and outgoing), unlimited text, fast data on each line. that $145/mo. total! . (In U.S. no surcharge for calling a cell.) If a line exceeds 2G of data in a month, pay $10 more for that line. [That only happens a couple times/year.