David and I go to Puerto Vallarta quite often and sometimes for as long as a month at a time. There is much to see and do. You can take buses anywhere, or taxis are very reasonable. Just don't use the taxis right by the cruise ship terminal because they are far too expensive (tourist trap for cruisers). The little yellow Nissan Tsuru taxis are great and very inexpensive.
One day is not enough time to see Vallarta. I'd take a taxi (to save time) to Galleria Uno, a local art gallery. They will give you a wonderful magazine called "Vallarta Lifestyle." It is full of maps,things to see and do. It also has excellent restaurant reviews to read.
Much of the best shopping is very close to their gallery. Los Muertos beach is an easy walk, south down the Malecon from there. You can enjoy the beach there and stroll around the Zona Romantica for more shopping and interesting people watching. Restaurant Row is right there too.
If you are going out to lunch I would suggest Le Bistro, River Cafe, Trio's,
or The Blue Shrimp.
Mariscos Polo (not pollo) has the best fresh-daily seafood in town but it is not fancy enough in decor for most gringoes. Polo, the owner is a wonderful man. His shrimp burritos and (my favorite) pulpo burritos are out of this world. I dream of them. If we are in P.V. for a month, we'll probably eat there at least twice a week. (8 times) He has great margaritas too. (No embience here, just great food and service)
If your ship doesn't leave until 10 or so, you MUST take a taxi to Las Carmelitas Restaurant. Get 6:30 reservations for a sunset dinner.It is the cab ride from hell but really worth it. This is by far the most fabulous view restaurant in P.V., but very moderate in price. The sunset view is like none other in the world, I promise. This is a true Mexican experience in a beautiful palapa outdoor restaurant. They grow their own beef. Their ribs are fabulous as is the whole fish. Service is fantastic. Tell your cabby to come back at say 8:30 to pick you up. You'll be back at the ship by 8:55 or so.
If there are other things you want to see, e-mail me or we can talk on the phone. I have lots of ideas about a couple of amazing beaches, favorite stores for shopping, etc. I'll be glad to help.
Most of all trust me that Vallarta is far more safe than any U.S. city. Do not be afraid to explore independently. Save your excursion money for Mazatlan, where there is little to see or do on your own, I.M.H.O. I'm going to P.V. from 8/19 to 8/24 for a visit with our best friends, Mare & Conrad. They are both retired doctors and are expates living there full time now. I'll give you up to date suggestions upon my return if you like.
Have a Margarita for me at Burro's Bar on Los Muertos beach if you walk by. Nice place to cool off and listen to some tunes.