There are some excellent gourmet restaurants in PV, but to enjoy them best, I would recommend them for dinner. That being said, dinners are leisurely and not rushed, so you run the risk of missing the ship when it leaves port. Sr. Mr. Pepe's was fabulous every time we went. It is a small, intimate, gourmet dining experience. They open at 6 pm and reservations are a must. The restaurant is in a house, up a steep hill at the south end of PV. You could do this if you really pay attention to the time; you would need to leave by 8:00 pm as you will need to catch a cab and get through town to get back to the ship. http://www.srmisterpepes.com/index.html
For lunch or dinner, we recommend Le Gourmet. It is in an old hotel, next to a pool with lots of flowers. Another very intimate, special place. It is at street level at the south side of the Rio Cuale. Great shrimp dishes and margaritas. We always order their tequila shrimp. Also, Las Margaritas at the south end of downtown - it was always excellent. El Set is great - south of town, a beautiful setting layered on the side of a cliff with incredible views. We had a tequila lime steak there that was unbelievable - we still talk about it years later.
For lunch, Carlos O'Briens has always been good and fun - it is in downtown PV. Dinner is a bit on the wild side. Chino's Paradise, south of town, is in the jungle and was very good as I recall. There was also a place south of town called Chi Chi's which was good and fun - another place built onto the side of a cliff. The dining area was right over a bay and had a beautiful view.
There are a bunch more, but these were places we would go when we spent a whole week in PV. Let me know if there are any you are interested in - here's a link: http://www.vallartaonline.com/restaurants/find/type-restaurant/?a=&order=restaurant&paging=0
Of course, there are plenty of places that are recommended by Carnival. Be sure to go to the port talks to see what interests you.
It is really difficult for us to opt for dinner in PV because we really like the main dining room on this ship. And, not to be missed, the strolling Mariachis board the ship and play in the main dining room during dinner. Dancers also board the ship at PV and perform The Mexican Folkloric Show with the Mariachis in the Taj Mahal - don't miss it!!!
Cab fare PV port to town is cheap, but I do not remember what it was last January and don't know what it will be when you are there. They have vans & Suburbans at the port that carry lots of people to town at a minimal fare. The return fare to the ship is reasonable, but be sure to get the cost up front before you get into the cab.