This time of year the heat is a problem. Ride early, stop between 2pm and 6pm, and cover your head -- I wear a white helmet with lots of ventilation.
Zaragoza is desert region. I did a ride from there down the Ebre river to the coast last month, and took around 6 days, including a rest day.
Mountains are where you might have to share roads with traffic. On the other hand, a lot of mountain roads are fairly empty if there's an autopista nearby with tunnels. I had some almost entirely to myself.
Michelin maps are good, and when you reach Catalunya you can use the amazing Institut Cartografic de Catalunya maps, which are world-class, and even mark footpaths.
The country is criss-crossed with GR routes, which are for hikers. Sometimes these are good for cyslists, but sometimes you'll end up pushing your bike or even carrying it.
if you're camping, you can't cook a anywhere right now. A dry summer has lead to a total ban on flames countrywide. But you're never too far from a small town or village, so you can eat there if you like. I recommend Menu del Dia, a cheap set menu available in pretty much any bar or restaurant.
I live in Barcelona by the way. Good luck!