Do you think the houses built in the 60s, and 70s have the insulation issues as well? Are you saying block walls are not good for this? (Again thanks for your help)
Block walls are fine, wrapping them with foam makes them better.
If you plan on NOT being there June - Sept. all of the info below becomes much less important.
Much of the heat gain comes from whatever is exposed to the sun. Roof's, sunlit walls and windows.
That's where it makes sense to install 1-2" foam to the outside of the block walls to slow the heat gain.
It costs $1500-3500 to wrap and stucco a 1200sf house.
Spraying 2" of foam on a flat roof and/or adding 12" of insulation in an attic helps, mucho.
Sun screens help and don't cost much in RP.
Energy efficient windows aren't a must but do help.
I would bet most of the houses built in the 60-2016's in RP and surrounding areas have little or no insulation unless it was added later.
You don't have to have insulation and efficient windows (many places don't) but it means keeping you place at 83 degrees and still having
a $200-300+ electric bill or adding decent insulation planting some shade trees adding window shade screens and be able to keep you place
5 degrees cooler and have a similar bill.
There are plenty of houses in RP with zero to little insulation in them, because 6 months of the year it doesn't matter as much. If you leave during June-Sept. having insulation isn't much of a factor.
So you don't have to do anything to what you buy, perhaps do something every year to slowly improve your house's energy efficiency.
Just make sure
what you buy is structurally sound because the other stuff is easy to fix or change.
Adding a mini split A/C with heat is the best way to cool and heat your house, much better than window A/C units.
(Mirage-2 ton unit good for 600ish Sq ft area cost approx $700 installed in RP)
Hope this helps.