Some 30 hours are better than other 30 hourses. Morrissey said that. And I say San Blas, three hours north of Puerto Vallarta, is worth the drive.
The beach is fine -- a dark brown sand beach with no one on it (weekdays, or when it's not Semana Santa) -- and a scrappy little town that's a hoot to spend time in. Particularly when one hour at the boozy San Blas Social Club turns to three, and the tequila bottle comes out. The bartender, Bernardo, is a tiny guy with a thick Hemingway beard, perhaps unsurprisingly considering he once was a bullfighter in Mexico City.
Much more to say, crocodiles and English poets for example, but will just sum up some of what I did in 16 seconds.