We visited Cuenca on a day trip from Valencia using the AVE train service - 200kms in 55 minutes incredible ! Its a beautiful place with several sights - a very worthwhile trip which we would recommend to anyone staying in Valencia.
1. The train tickets are relatively cheap if booked well in advance - we booked from England using loco2 whose website is much easier to use than that of RENFE.
2. The AVE train station is new, very modern and situated a few miles outside Cuenca . There is a bus to the Old Town costing 2.15 E's which leaves every half hour or you can take a taxi costing 12 E's ( set price).Ask to be dropped off at the Plaza Mayor.
3. The Tourist Office( with helpful English speaking staff) is there and you can pick up a map and details of the opening hours of all the attractions. There are a number of good value cafes and restaurants on the Plaza and the surrounding streets.
4. We visited the Cathedral ( entrance fee but that includes the audio guide ) - excellent, the Museum of Abstract Art ( free for everybody) - excellent and the Science Museum ( free for seniors) also excellent with several interactive displays and a Planetarium.
6. We walked up to the old castle ( now just a ruin ) where there are fantastic views over both river gorges on either side of the Old Town. The walk is uphill but it was not unduly steep - however there is also a Tourist Train if you don't want to walk.

This is a wonderful town to walk around although very steep in part. The cathedral is exceptional in its antiquity.

So much to explore in the old city! I've been numerous times since I got here over a month ago and every time is a new adventure! Well worth several visits at least! Many museums, restaurants, and shops available in this area, a theatre, the St. Paul Bridge, etc...