The Beijing airport also has kiosks where you can buy SIM cards, so you could buy a card immediately after you got through customs if you wanted to. The kiosk clerk's English was better than that of the clerk at the store where I ended up buying my card.
Make a connection
Unfortunately, I wasn't able to make a data connection with my iPhone 3GS and its new SIM card the night I bought the card—I kept getting a black screen with a message in Chinese, and Cancel and Accept button that didn't work. Obviously, my data plan had not yet activated, but I didn't know whether there was a problem with the SIM card or with the phone's setup—or whether I just needed to wait. Since the China Unicom store was closed by this point, I had to wait until morning anyway.
Luckily, the next morning the data connection worked. I could connect to Bing, Apple, and (unexpectedly) Instagram without even using the VPN. I couldn't connect to Facebook or Twitter, however, so now it was time to try a VPN. After I waited for about 15 seconds while the phone established a connection to AirVPN, a VPN icon appeared in my iPhone's status bar, and I could connect to Facebook and Twitter and read both feeds, as well as post my own messages. I was also successful using ExpressVPN. While I was using a VPN, I noticed a network lag of 4 or 5 seconds, but it never got worse than that.
I was in Beijing for four days, and I never had a VPN problem. I was surprised to find that the signal strength at the (physical) Great Wall of China was very good, and I successfully posted Instagram pictures from there. I use Facebook to record the places I visit, and I was able to check in without a hitch. I also used Apple's Maps app to see my location relative to other Beijing landmarks (though I didn't use it for directions). And I kept track of the scores in the Major League Baseball pennant race that was then going on.
The only annoyance I encountered was that every time my iPhone went to sleep, I had to reconnect to the VPN after waking it up, before I could use the data connection. That process takes only takes a few seconds, but I wish there were a way to make it more automatic.
The next time
Apart from not being able to use the SIM card's data connection during the first evening, I didn't expect everything to go as smoothly as it did. Of course, since the Chinese government is actively (and endlessly) trying to prevent the use of VPNs to access the "outside world," it's possible that at some point the VPNs I chose won't be able to provide their services in China. So for my next visit to Beijing—if there is a next time—I'll have to be prepared to use other VPNs, just in case.
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