I don't know why you are all running down Acapulco. I have been there a bunch of time, most recently for a month in July, with no issues whatsoever. The reality is that with the exception of Puerto Vallarta, no place is really insulated from the issues. As for saying even the Mexicans aren't going down there, that's a crock. I am over by Caleta & Caletilla and the beaches were packed 2-3 umbrellas deep every day, with buses from Mexico City hogging all the parking.
All three places have their charm, and all three are worth visiting, all are different experiences. If security is going to be your overarching concern, go to Puerto Vallarta.