We have been to PV a few times and have done a few \"Booze cruises\" which usually include snorkeling, horseback riding and beaching. On almost every tour we have been able to see whales. Some very close, others not so close. We also have been on an eco-tour where you go out on a scientific tour in a Zodiac boat and they teach you about the whales. This tour even broadcast sounds under the water to try to attract whales. Sadly, on that particular tour, the \"party boats\" got better views than we did. I found this site online(-www.puertovallartawhalewatching.org) that will help you out greatly in deciding what tour to pick.
Good luck!

T