We had an overnight stay at Cadiz (Seville). Quite a number of fellow passengers took the train or bus to Seville. That would be a good option if you are willing to walk 20 - 30 minutes to the train/bus station in both Cadiz and Seville. The ship offered land tours of $179 or $199 to Seville. HAL does not offer a tour with just transportation like Celebrity did. However, since it is an overnight stay at Cadiz, some passengers chose to spend the night in Seville, which was a wise choice for people who had not done Seville before. At the Cadiz pier, Radio Taxie offered fixed price round trip taxi fare to and back from Seville - 4 hour stay at Seville. For seniors who want to see Seville on their own, or for passengers who want to swing by to see Seville without waiting for the next train/bus, this would be a good option. Afterall, the cathedral and Alcaza and the Barri Santa Cruz area are next to one another. The taxi option is about 3 times that of the train/bus. The popular 5 p.m. bus was full and people had to switch to trains. Thus for the do-it-yourself folks, take this into consideraton if you ship does not stay over night.
With the taxi option, it would be possible to visit Rhonda and/or Archos de la Frontera - the white towns. Unfortunately, I was not aware of the taxi availability. From USA, I called Radio Taxi and noone spoke English. I got quotes from various vendors and they wanted to charge 450 - 1000 euros for a 7 - 8 hours tours. In addition, advance payment for the full amount, non refundable. Even people who had visited Cadiz before were not aware of this taxi option. They are just outside the pier and the fixed pricing is posted right there.
Since I was not aware of the taxi option, I had already booked HAL's White Village tour (i.e. in lieu of Achos de la Frontera). It turned out to be a very relaxing and enjoyable tour. Vejer de la Frontera is on a hill and the views of the green landscape surrounding it is very soothing. The guide was wonderful and led us to a very informative walk of the village. We drove along the Atlantic coast and visited a seaside town of Conil. Though not a stunning town, Conil let us take a quick feel of how locals spend time on the beach. Some passengers enjoyed coffee or beer or wine in the restaurants.
A few daring do it yourselves used the bus to Vejer. I did check it out before the cruise. But with ONLY one bus returning to Cadiz in the afternoon, it would have been too risky for me.
After the White Village tour, I still had time to stroll in Cadiz old town for 3 hours (ship did not sail until 11:59 p.m.).
OVERALL FOR CADIZ- there are many options. Some passengers just spent their days walking around and relaxing on the seaside plazas. Some went to Seville overnight. Some took land tours HAL. For do it yourself folks, check out buses/trains/taxis. Shopping was supposedly good too.