You can do these ports on your own.
Valencia is amazing.
They have a super new cruise terminal and its just a short stroll to the local bus that will take you into the City. After a stroll around the "Old town" you can catch the Hop on Hop Off bus, which has a commentary, and get off half way and gaze in awe at the new buildings that look like works art.

A river used to run through Valencia,but they diverted it ,to stop the flooding ,and were left with a ribbon of amazing Real Estate that has ,and still is, being developed.

Barcelona also has new Cruise terminals and shuttles take you through the port to the start of Los Ramblas. You can stroll,or push your way through the crowds,up this busy street and about half way up is the Old part of town. A local guide would be great in this area as you can get lost very easily. They also have a HoHo bus that visits all the major attractions and sights.We hopped on , but we did not hop off as it was so busy we did not think we may get back on again.