thehays,
Availability is gonna vary, it is on the increase, but believe me, there are a lot of places you will NOT have wifi.
As you can see by Gruffy's remarks, even when you have it, there can be trouble in wifi heaven.
Internet on the road is a challenge and the availability is changing faster than I can type this response.
Do a search here on the MOC forum, we have had any number of discussions on just this subject and some as recently as this last weekend.
Free, yes, free, no, free, sometimes, this also varies.
Since Al retired 1/1/2001 we have tried to get away from Michigan winters, and specifically Michigan March, ask anyone who knows me, I HATE MICHIGAN IN MARCH! ewww.
Anyway, the first year out, went to Georga, South Carolina, North Carolina, Virginia. No cell phone internet, no wifi, no cablenet internet, a few campgrounds would provide you with a phone line if you had a service like AOL, and a local number, please limit your online time to less than 15 minutes, or 30 minutes. Went for 10 days or more with no internet, no email, then had to go to public library to get online. There was even one library near Norfolk Virginia that still had NO internet in late March 2001! NO KIDDING.
This year and last, we are on a cable net internet, last year it was shaky, this year, same service, MUCH better. Free at the campground, but this place is not cheap.
I have yet to hit a campground that has WIFI, but Steve R and others have hit a LOT of campgrounds that do. Some of the availability is in how you pick your campgrounds. We pick where we want to go and live with what ever we are faced with, cell phone, no internet back to the library, whatever. Others, pick their campgrounds by what services are available. That is a personal thing, nothing wrong with either way.
Our advice, be prepared to use a lot of differennt modes of connection. Some even like a Satellite right on their unit. And just discussing "S" in a RV could take up several hours of typing!
Good luck and have fun!
Carol