Rooms Deluxe should suit you perfectly. It's a couple of mins walk to the City of Sciences
www.roomsdeluxe.com
We got a better deal through booking.com rather than direct.

This is what I said here last year:

Just spent 5 days in Valencia staying in Rooms Deluxe. Each room has been decorated/styled by a different local artist - we had the surfing room. Quite plainly furnished,Air con. Beds were comfy, TV had french & Italian channels and CNN. Some of the rooms are very opulent, some extremely weird (eg The swimming pool room): Its pot luck what you get,which I suppose is half the fun!!!
There is a well furnished lounge with TV and DVD, a well equipped guest kitchen- with fridges/freezers and cupboards for storage. 3 computers are available here too. ( Free usage). Free Wifi also - though the wifi on our floor was being fixed while we were there. I did manage to connect via an unsecured network though!
The price per night was €70. The location is just metres from the no 35 bus stop(€1.25 and 10 mins to centre).A few hundred metres from the City of Arts and Sciences. A Large Carrefoure and a big shopping mail are also just a couple of mins walk away.
We would stay again.