Depends upon the park.
Basically the farther out in 'nature' you are, the more difficult it is to get wired internet. And wired internet is always more reliable than anything WiFi over the air solution.
Most RV folks use an over the air situation, connected to a hotspot tied to a major carrier wireless plan. This can vary from barely functional to streaming quality - depending upon how close to cell towers and some other things.
Also, 'Unlimited Data Plans' mean the company will not charge you more money no matter how much data you use. It does not mean that your data rate will not be throttled if you exceed a certain amount of data - ATT, Verison, T-Mobile all do this, and they also impose limits on data transfer rates for companies that resell their service.
Some long term parks had wired cable systems which can provide internet. Not many though. Parks marketed to a mobile RV population seldom go to that expense.
I've seen a few places where long term residents had installed fixed dish satellite internet systems, mostly with good results.
It has to be something you ask about as you look for a 'home'.
Full-Time 2014 - ????
โNot all who wander are lost.โ
"You were supposed to turn back at the last street."
2012 Ram 2500 Mega Cab
2014 Flagstaff 832IKBS TT