New Member to Forum

You really should visit and look around.  After much research I ended up living on the east coast in Humacao in a community called Palmas del Mar.  Puerto Rico comes in many flavors.  Start by making a list of 'must haves.'   Most folks who are new to this forum hear about Rincon and think that is the place to live.  It is worth putting it on your checklist, but there are many other wonderful locations that may better suit your needs.
Medicare is accepted all over the island. 
Wherever you land, you need a car to get around the island.
There are many places to rent, depending on your budget.   Also, the economy does not seem to have any impact on most people who live here.  Will it really make any difference in your everyday life?

The three main issue with living very close to the sea are:
1) potential flooding during a storm if at ground level, same for your car. At least 15 feet above sea level you should have very little issue.
2) humidity, PR humidity hangs around 75% most of the time and occasionally it hits 98. If too close to the sea the waves frost tend to be soak up by the air so more humidity in the air which can cause your clothing to mold. If in contact with medal may end up with rust spots. People say they feel their clothes are all way damp when next to the sea.
3) Rust, metals rust when you are close to the beach the most. Salty air and humidity bring rust. Cars, barandas, hinges, anything metal is affected to some degree by the salt or the humidity.

Read thru the forum, but we are here to help, also keep in mind your physical and medical state when selecting a location. Take several trips to the island and try different areas. If you have difficulty walking, do you want to walk up or down hills?

Spanish IS A MUST LEARN, while about 1/3 of the population knows some English, in many occasions you will not be around somebody that speaks it or speaks it well enough. There are about 3.5 million people in the island you need to be able to speak with any of them you encounter at doctor, road, supermarkets, pharmacy, DMV. If you do not learn Spanish you will likely be isolated and lonely and will miss on the charm and culture of living in the Caribbean.

I know very little about MS, so you must consider how often you will need more than a regular doctor and how far you are willing to drive for the special attention you will need.

You can find places to live for 500-700 a month rent in most of the island some will and some won't meet your needs. Tourist areas will likely go for $900 to $4,000 a month.

The island is 100 miles long by 35 miles wide. Anywhere you stand you are never more than 18 miles away from the sea as the bird flies but maybe twice that by road due to how streets are payed out and altitude.

During winter time it is hard to find a place to rent for short periods of time like a month. I would suggest something like airbnb but it would not be cheap for a month. They tend to be 50 to 200 per night and that adds up when it is a month stay. Regular places to rent for a month will not work for you since you will likely get an EMPTY house or apartment. Few have refrigerators or stoves and most don't have furniture. Airbnb like places are fully stocked with everything including beds, couches, chairs, plates, pots and kitchen appliances and utensils.

You are going to need a rental car, also check with your current insurance about coverage for a rental car otherwise the insurance at the car rental can eat up your budget.
Rey

Like Frog said, there are lots of very lovely places on the island. It is very diverse:  from the historic, colonial charm of Old San Juan to modern, luxurious condos to country homes and beach retreats. If you're still in the considering stage, I suggest you come on down, rent a car and just sightsee. Their are hidden gems all over the island.

I picked Old San Juan. I can wake up to the sound of ocean waves and walk to restaurants, beach, shopping, museums, music, parks. It's a city within a city, in a way, in that it has its own character and 500 years of Spanish history. Nothing on the mainland compares to it. 

Depending on when you plan on coming down, my apartment might be available for rent. I rent it through AIRbnb. It is fully furnished and equipped.