Idea for Proposing in Puerto Rico
On the West Coast of the island hop a boat tour to see the whales and pop the question in the middle of all the excitement of the whales surfacing.
From Ponce, if you head toward Aguadilla ( I think it is Road 2) you will see Aguadilla Mall on the left (with a movie theater in the parking lot) and not to much farther up on the right will be a place for you to pull over and there is an overlook that looks down the cliff and out onto the water, supposed to be a beautiful sunset from this spot.
Near Aguadilla is a beach called Crash Boat (picture above), rent a boat and take your love for a little ride, maybe some fishing and pop the question with Puerto Rico as the backdrop.
On the Northwest corner of the island is a place called El Tunnel (picture to the left) beautiful tunnel you can walk through (trains used to use it). Walk through the tunnel, past the rock walkway and out onto the beach where if you look closely there are crabs, etc. everywhere. Not many people go out here, so it is pretty private. (See the picture at the bottom of the page, with my fiancee in it.)
In San Juan you can go to the Park of the Pigeons or any of the plazas where the kids are throwing corn and pop the question it in the middle of the square, with all the people as your witnesses and the pigeons flying around.
Take your love to the Rain forest just southeast of San Juan. Go for a hike and pop the question on one of the bridges with the water in the background or in one of the towers.
If your loved one loves earty stuff, try proposing in the Camuy Caves.
If your loved one loves science, go to the Aericibo Observatory and propose next to the big dish. (Was in the movie Contact.)
In Ponce, you could do it at the top of the huge cross museum, if she is really religious.
Not my first choice, but there is a square next to Parque de Bombay in Ponce, where the pigeons eat. That could be a sweet spot if you are feeding the birds.
Inside the main fort at San Juan, you could climb to the top, where you get a nice overlook of the water and the surroundings. There are usually tons of people up there, so you are sure to get a bunch of "awwww" from everyone.