Kkyllo, the other posters pretty much described Holbox accurately. I don't know Mahahual. The only thing I'll add to the Holbox discussion is that you wouldn't necessarily have to take a 2nd class bus. The better hotels should be able to arrange transfer at least to Chiquila, tho it will certainly cost more. I see that now there is an express ferry from Chiquila? Indeed, Holbox is becoming more popular. On one of our visits, our hotel sent a lancha to Chiquila, and it deposited us on the beach in front of our hotel.
http://www.holboxisland.com/
And Stew, regardless if Zihua gets more national than foreign tourists, it is still the 3rd most touristed Mexican beach destination. That would hardly make it the PDC of twenty years ago, which is what the OP is looking for. More like the PV of 20 years ago.

<Zihua ... is still the 3rd most touristed Mexican beach destination>

Wow, didn't know that. It's surprising...

I would have figured Cancun, PdC, Cabo, Mazatlan, Vallarta, Acapulco were all more "touristed" than Zihuatanejo.

I was kinda surprised too. Wikipedia puts it behind PV and PDC, as I noted in my earlier post. https://en.m.wikipedia.org/wiki/Zihuatanejo
I think much of that is due to the semi-recent (2007?) completion of the Morelia toll road. Plus I think folks from Mexico City may be preferring Z/Ix over Aculpulco in recent years.

My bad, I should have said Cancun, not PDC.

Spent time in PDC as a backpacker in the 70s and again with the kids in the 90s, so I know what you're talking about. They surely paved paradise there. If you do venture back to the Yucatan, my fave beach town there is Tulum.

Of the west coast beaches for even better ambience than the PDC of old, I would vote for Sayulita, the coolest surf town in Mexico. Wonderful plaza, laid back dining options, several excellent shops run by Europeans who have settled there as expats.

Also consider Todos Santos, a tiny town with lots of old world charm about an hour south of Cabo. The issue there is that there are few swimming beaches right in town (too rough), but if you have a car you'll be fine.

Surprised nobody has mentioned Puerto Escondido -- remote, mystical, growing, but not overly touristy (although I haven't been there in years). You can combine a visit there with a trip to Oaxaca.

http://nymag.com/travel/2014/winter/...exico-2014-10/