I would actually advise against Playa del Amor. For starters, it’s not that near Puerto Vallarta. You can get an all-day boat to Islas Marietas from PV or Bucerías, but it’s a few hours so most are loud, open bar party boat rides that’ll let you SEE Playa del Amor.
The closest town to go to Islas Marietas from is Punta de Mita, and that’s 1.5-2 hours away from PV by car. The tour operators said that if you want to actually go to Playa del Amor, this is the only place you can book directly from. Asking around in PV, this seems to be true.
Playa del Amor can only be visited by something like 300 people a day. Only 20 or so at a time, so you have to buy a special permit in advance in Punta and, even in low season, they’ll often be gone before noon. If an Islas Marietas boat tour is 600 pesos, for example, inclusion of Playa del Amor more than triples it to 2000. For 15 minutes access to a beach that, in the age of social media, has basically just been turned into selfie central. One thing I’ll give it is that, getting there is pretty cool as you have to swim in (not underwater, though, the entrance arch is quite high).
I took the Islas Marietas tour without Playa del Amor, and that includes another island, called El Cráter, if I remember correctly, which is very similar. Higher walls, which allow the boats to go inside. The main difference is that it doesn’t have a beach so you only get to see the crater from the water. All in all, I enjoyed the tour but think Playa del Amor wouldn’t be worth it.