I normally use a Verizon air card simply because campground/park wifi is so unreliable. But if there is decent connection available I'll use it for anything. First I make sure that there are no similar looking SSIDs. If in doubt I'll ask the office to verify. Not so much a problem at campgrounds, bigger problem in airports, malls, etc.
Next, if I'm doing financial transactions I always check for the https connection before I transmit any sensitive info. That encrypts the data from my laptop to the financial institution.
Third, is it really worthwhile for a hacker to hang around a campground on the off chance that 1 or 2 people will check their bank accounts? Doesn't seem to be much payback there when they can go after places like Target and Nieman Marcus and get thousands of credit cards.
I know of one couple who had some passwords stolen when they used a library terminal, never heard of anyone hacked while using campground wifi.