Internet for 4 months

Verizon offers a mobile internet device with various data plans. Not tied to your phones, independent. We receive internet in places that cell phone don't work. Different signal for data devices. If you are going to be in a rural/remote area, I'd consider a stand alone device. If in a city, there's lots of choices with a cell phone.

We use a T Mobile prepaid hotspot. We pay for 6G of 4g for $25.00. After the 6G is used; you get unlimited 3g. If there is 4g available you get that as long as it doesn't slow down others.
We've been using this for 2 years. Stream Netflix with no problems.

We live in Springfield. We camp at the coast in the winter and Central Oregon in the summer. No problems. KEN

Nomad internet is month by month, unlimited data. Not cheap

We cut the cord many years ago and use cell service at home and on the road.

Use the wifi at a restaurant to download a few movies each time you stop for dinner. Netflix and many other services allow you to download for future viewing.

Cell based hot spot. Unlimited with throttle at 2 m/s. It is often 0.52 m/s. If high speed is required--count on about 3 gigs per day.

Best bet is get your own dedicated cell "hot spot" or use your phones data and use your smart phone as a WiFi "Hot spot" to connect a laptop or Tablet to it.

Forget about using ANY campgrounds for streaming through their free WiFi, chances are you will have enough trouble fishing emails of of campgrounds WiFi let alone streaming TV shows for more than a few minutes at a time. Most campgrounds WiFi systems are not all that good and they often get pretty busy.

Barring all that, perhaps rethink your streaming TV thing, some streaming services allow you to download programs for a specific time limit so you can watch at a later time without Internet connection..

Otherwise, rent movies on DVD while visiting, or if you have movies you have bought, rip them to a external hard drive and take the external hard drive with you.. Some external hard drives have built in WiFi sharing capability so tablet and laptops can connect to the External HD via WiFi.

Find an RV park with good wifi. Or pay your relatives to upgrade their service.