Worried about online banking on public wifi? I would contact the bank for advice. Bank websites always encrypt data going both ways (as indicated by https in the address) so it may well be as free of risk as using a credit card. Here in Canada banks have a good record of absorbing the costs of all fraud unless the customer has been extremely careless with the password.
Public libraries are another source of free Internet away from home. In Canada our government pays the bill for every library to provide it, on library computers or your own via wifi. On the road it is pretty easy to find the library in a small town and it often leads to a nice conversation with local people.
I also find cellular Internet costs too high; I use a pay as you go service without Internet on my iPhone 5 for about $100 a year while others pay $800 a year. I know many have pressing need but I am near wifi 90% of the time so it just isn't worth the cost.