Humm, I have T-Mobile (6GB per line with data stash), the last 2 times down this month, I was able to watch Dish anywhere from my laptop
to my 42 inch TV via a HDMI cable and was getting 700k-1300K pretty steadily using my phone as a wi-fi hot spot. (looked like 720P resolution to me)
There are times when a lot of people are down that it will become really slow and a no go for streaming.
I don't know about the 3 month rule phone use for use in other countries.
When I plan on being down in Mexico for long stays I will just get a Telcel Sim card to put in my 2nd Sim slot for phone service and not worry about it
and get whatever Internet service is available.
For Internet options, you are pretty much limited since RP is, 10-20 years behind the USA for Cable TV/Internet type services.
So you options are currently
Tel-Mex - OK to slow. Supposed to be 1.5mbs (gets really slow during busy periods)
Dish TV Internet can be expensive
There's another Internet provider using a dish,
Thread link-
https://www.rockypointtalk.com/threads/satellite-internet-access.9718/
IZZI was rumored to be coming to RP 18 months ago (cheap TV and 10 mbs internet service for $30 per month) but I haven't heard anything lately).
I'm going to detach from the Internet and just enjoy what Mexico has to offer when I'm down for weeks at a time.
I look forward to not being connected all the time when I'm down.