I just rode the EV8 from Barcelona to north, so not the route you are planning to take. The first 100km from Barcelona to around Girona were without any sign posts, but the chosen track itself (got it from biroto) was ok. A lot of it was dirt road, some in good some in not so good shape. EV8 then goes along a pretty well maintained route (Pirinexus / Vias Verdes).
The track from biroto seems to follow mostly smaller roads towards the south and is pretty close to the sea at most times. At least in Catalunya the drivers are very respectful and keep their distance from bikes. In cities you will often find dedicated bike lanes.
At least up to Valencia you will always have a train track near by.
The larger roads (N- prefix) usually have a pretty wide shoulder, so they are also be an option sometimes.