Day to day and sometimes month to month some of the members disappear for a spell. When it comes to mainlanders the West is very popular, more so than the East of the island. I view the west of the island as more California coast like, rocky beaches, big waves, young people walking around in swimsuits going from bar to bar and lots of small restaurants with English menus. While it is more lay back in other ways, it is quite the spot for entertainment. During winter all the snow birds flock in and is busy, during the rest of the year it calms down a bit. Also prices for properties have gone up quite a bit due to all the mainlanders moving there and English is almost as useful as it is Spanish there.
The east side is more day to day, working people and we have a lot of mainlanders also but not as many. East coast attracts people who like to be traveling to other islands, do boating, do scuba, snorkeling and be close to San Juan. Condado, Isla Verde have a lot of tourists and mainlanders but that is north-east and the prices are high.
Beach front means people in front of your house since beaches in PR are all public property. your property ends and the beach starts, but the beach is not yours and can not be fenced. Depending on the spot, you may see thousands of people a day or 1 or 2 a year. If you try to limit access you will likely end up with a protest once people notice the limitation. Flooding as you stated, salt spray causing lots of rusting of any metal and your car. Also a lot of properties do not have any sanitary facilities, they dump the raw sewage into the sea, so you may have bacteria issues with the water and things floating that you may not want to swim with.
A lot of people feel safe country side, more so because there is little reason for bad guys to be anywhere close to your home. Locals if you make friends with them will keep an eye on your place and they will do that if you interact with them.
Bochinche (Gossip) is very common in PR, but they have nothing to say if they are not watching out the window, this is both positive and negative, they will know who was taking mangoes in your property and they will talk about how you dress or if you have a lover that visits when your husband is out. It is like that bar, where everyone knows your name, just ask anyone in the street where "Doña" Sonia lives and they will give you directions or offer to take you there. But Bochinche is everywhere not just in the country side.
Don't go showing you are rich or have expensive things and you will have no reason to be a target. Learn the language, be friendly, be part of the community, attend church, volunteer, you will make friends and the people will keep an eye for you. Not only that but they will show you what to do, where to shop, what time to arrive for the specials, where are all the hidden river spots, and exchange fruits and vegetables with you.