We give up on the campground poor and crowded WIFI connections pretty quick. Public access WIFI also just didn't seem to be the thing to use to pay bills online anyway.
We went with the VERIZON SECURED MIFI PLAN which was a 3GB DATAPLAN and cost around $27 a month. This creates my own WIFI HOTSPOT around my trailer where I can connect up to five of my WIFI enabled devices. This works out great for paying bills ONLINE, checking emails, checking-in with the kids, some web surfing, etc. If we was to get into movies or TV STATION downstreams then the MILLENICOM 20GB Plan using the VERIZON NETWORK would be the way to go. I can't imagine anyone using 100-200GB of data... Most plans I have seen max out around 20-30GB of data costing around $70 a month...

photo from Google Search
My VERIZON MIFI stand alone unit normally sits in a WILSON SLEEK CRADLE which has its own outside antenna. Being a small shirt pocket size unit however when we want to go sit at the beach or even just go hiking I can carry the unit in my shirt pocket and all of the tablets etc we have with us works like a dream...
The MIFI PLAN idea works out great for us in our travels around the Eastern side of the US.