you do need to correct your map's placement of I-5, it is a North-South Freeway as evidenced in the first trailer, as well as all US highways (trust me, I live on that exact highway).
This might explain why you don't agree with me about where Puerta Del Sol and La Puerta are. Interestingly, after scanning through your flickr, reviewing the first trailer, and observing many of the screenshots, I can identify 10 to 20 shots of the interchange that shows the sign that says Vespucci, Puerta Del Sol, La Puerta, and Maze Bank Arena. As the only two things between Vespucci and the Arena (as there are none visible to the north) on the west are Marina Del Rey and the Airport and Hotel area before it, I don't see how your placement of Marina del Sol (which has no evidence at all) is particularly applicable. I'm sorry this sounds like b****ing, but I feel your dismissal of what I have surmised (three parts of Los Santos and two Freeways) as speculation, when Marina is a guess and the La Puerta Fwy (I-5) is wrong on your map is a little insulting. I respect you, but I feel I gotta call you on this.
Lastly, Puerta and Puerto are different in their meanings, by the way. As R* has shown me, they know about some pretty obscure Spanish (Paleto, which not one of the 7 or so native spanish speakers I work with have ever heard of). Puerto means port and that is pretty much it's only meaning, where as Puerta means door, gateway, or entrance. Puerta could be used here as a Puerta Del Sol as Gateway of the Sun, which would fit much more with an east or west facing location like Marina Del Rey and not a south facing location like the Port of South Los Santos (which has a Los Santos Marina and Los Santos Docks). La Puerta could easily be the area around the Airport, meaning the Gateway, in reference to it being the area between the city of Los Santos and the Airport.