Can I restrict Nexus 7 2013 LTE to 2G/3G, instead of just 2G?
What version of Android you currently have on your Nexus device?

I have (I think) exactly the same device, as you (ASUS Nexus 7 II (2013) LTE) and three days ago it was upgradred from 4.3.0 to 4.4.2 KitKat (I issued manual upgrade, by connecting to WiFi network and going to Settings &gt; About phone &gt; System Updates).

After upgrade, option you're referring to (Settings &gt; Wireless &amp; networks &gt; More &gt; Mobile Networks &gt;  Use only 2G networks) has been changed to Preferred network with options: 4G, 3G and 2G.

Now you can fully control, which kind of network your tablet access and you can limit it to use only 3G networks (second option), which has full fallback to 2G network, if 3G one isn't accessible in your area.