I’m going to have a week in Sitges near Barcelona in November is it worth taking the bike to ride in Parc del Garraf area?

Yeah, there are some good trails around there. Some of the local guys have been adding stuff to trailforks recently which should help you find some trails.
A friend of mine, Markus, runs a rental and guiding company (wild coast bikes) just up the road in Castelldefels too if you wanted to rent a bike instead of bringing one along.