Most of us find ourselves having to work on free Wi-Fi, but public Wi-Fi networks are unsafe -- particularly that it's very insecure. Even if a Wi-Fi network has a password, that doesn't keep you safe from other people on the network. It's notoriously easy for any of them to see what you're doing and, in some cases, steal personal information or passwords.
If you do need to work on a Public Wi-Fi then we suggest checking with the shop/restaurant you are in by speaking with a staff member to make sure it is their supplied Wi-Fi, also making sure you have a Firewall in place on your computer before connecting and that it is enabled on its strictest/highest setting. And if possible use a VPN connection to encrypt traffic.