most porn people lead normal lives when they're not working and unless they personally invited you to meet them someplace, probably wouldn't want you to try to find out where they hang out by means of forum posts.
And what will you do when you show up and find them there? They might give you a smile and a picture, but they're not going to fuck you, or fall in love with you, or start sucking your cock right there on the spot.
It would be way less creepy of you to hit up your fav porn girls and ASK them where they will be and if you can meet up with them there, although I'd assume you probably won't get the answer you're looking for out of 95% of them.
Also, if you only have 4 days in LA, the valley is the very last place you would want to spend ANY of your time! The weather is horrible..it's a dirty and rude place to be! Go to Santa Monica, go to Hollywood, go to the beach, enjoy the sunshine, have a real vacation! Instead of trying to stalk down porn girls:/