We went to Acapulco this past March. Very disappointed with Acapulco. Opted to stay at a beach hotel (The Condesa Fiesta, or something like that). The sun was great, and being right on the beach was nice, but we didn't like the nightlife (of the little there was). We did have some wonderful meals at restaurants overlooking the bay. Did the obligatory divers cocktail thing (viewed from the restaurant, though we just had cocktails), then the divers came over to meet us after (and get their picture taken with us). As for the city, even walking along that main road by the bay was scary at times.

All in all, we would say the same as your friends: there are better places in Mexico to go for surf and sun.