Around here Lowe's, Target, Winn-Dixie (super market), McDonald's, Starbucks & the various local coffee shops, lots of restaurants and Walmart offer free WiFi. Xfinity WiFi used to be free for anyone, but now they do require your username and password to surf.
As has been said, paying bills or doing any type of secure transactions on an open network is risky. You can get pay as you go 4G mobile hotspot devices that would be a more secure alternative than an open network. When we are at a campground and need to pay bills, etc. I always use my Droid Turbo as a mobile hotspot if the campground has an open WiFi.
-Michael