That's my favourite method to buy BTC, meeting up with the seller (also,the safest!)
I think that public WIFI are threats to the security of our accounts. Hackers might have an access to our personal information that we entered on our device as well as our accounts. I didn't advice to trade using WIFI connection that we're not sure if it is trusted or not.
100% right public WIFI are not protected and have less security, which makes hacker to hack easily and can check all details of whom ever connected with public WIFI. It is much better to use your own internet and then do the transaction. About local transaction use public places like Mall, Pizza corner and do dealings in the busy hours so that their will be lot of users nearby so you can be secure.