Muy Bien!
restaurants in CaboPuerto Vallarta RestaurantsWhen I travel I rely on concierge recommendations which typically work out great. On a cruise ship you will have plenty of sources of good information but you might suffer from the swarming when the whole ship disembarks at one time... I've never been on a cruise but I was in Cozumel and other places in Greece when cruise ships would come in. You might want to try to plan a bit ahead so you don't get stuck wandering around the touristy areas and actually get to see the areas that the rest of your fellow travellers might not get to. If it were me, I would head right out of the crap port area and head for old town or "downtown" areas... of course I've never been to the places you are going to but I think the port situation is pretty much the same world wide, the pits.
I really like the Eyewitness Guide series. It's a very basic reason why I like it... it has pictures next to the topics and you will be able to identify what you are seeing very easily. Other tour guides give more information and history but these are great for getting around and for looking to see in advance what you'd like to visit.
Eyewitness Guide to Mexico This may not be very specific to places you are going... I typically like the ones that are by city rather than country but couldn't find one.
The other really great travel book is Lonely Planet.
Lonely Planet website on Mexico Try clicking around that site and see if you find anything good. I didn't see a lot on restaurants but I'm sure they have it in there. It's written by Aussies that travel all over the world and pretty good source with down to earth information.
If it's good Guacamole you seek, I don't think you are going to be disappointed... the food in Mexico is really great. Just be careful not to let the hawkers drag you into their sleeze bag restaurants... you find out where to go and then go there and do not be swayed to go into any old place or you might be sorry.

You are going to have a great time! Hope this has helped... the best restaurants are always in old historic buildings but they should have some credentials displayed in the window like Frommer's ratings and awards... don't try Mexican dive restaurants or you might ruin your trip.
Also, remember to ask around what cab fares should be before you get in a cab. A lot of times it is wise to make an agreement to the fare before you get in the cab. It's not like they will rob you blind but you might get into an argument with a cabbie and that's not very pleasant.
Buen Viaje!