It was walking and bus. We did quite a bit of walking, but it was on level ground and we walked at a slow pace. The one exception was when we climbed to the top of the fortress. Our guide was 79 years young and hardly broke a sweat. Can't say as much for myself! I would say the majority of the people didn't try it. There were vendors near the bus where you could shop a little.
Puerto Limon is one of our favorite ports. We love the rainforest. The last time we did a ship excursion called "Tortuguero Canals". It was so great that we booked it again, and enjoyed it just as much the second time. We enjoy seeing wildlife in it's natural environment and nothing compares to seeing monkeys in the rainforest!
After the tour we were served some very good snacks and fruit. Everyone has different expectations for their excursions, but this is one that we really enjoy.