There are a lot of "hacker" kids which may just try and succeed hacking any size of fish floating nearby just by an accident. So, obvious security measures, mentioned by chaosmagnet, should not be ignored, as well as a basic security threats and practices knowledge (i.e. change your password often, cover the keyboard typing the pass in public).

For the free (such as "cafeteria") wifi - I wouldn't be too concerned. It's usually too weak to efficiently brute force and download something significant, randomly searching strangers, or to deploy a targeted attack. Just not enough time for the given bandwidth. The typical hack of such a WiFi hotspot would be to fake their proxy server. But google browser will immediately tell you about that (not so sure about stock IE, though), just don't be ignorant to messages on the screen.

VPN is definitely beneficial to reduce your communications exposure, unfortunately it's quite complex solution for a newbie and have serious impact on performance of internet device.

Chisel, "Remote PC" Android notification might stand for the PC being discovered over BT or NFC (as a potential data exchange device), not necessarily as an act of unauthorized remote access.