John,
Rights of Way and Ordnance Survey maps go hand in hand in England. If it's on the map as a right of way then we can assume that it is a right of way. Many is the time that I have walked along an ill defined route just waiting for the shout "Oy, get orf my land!" I'm ways ready with the map to dispute the accusation and demonstrate the facts of public ownership. It helps so much when you can speak the language and understand both arguments. In England many "Rights of Way" have been eroded and planted over by farmers who, understandably, don't want the hassle of leaving a diagonal path across remote fields. It remains an emotive problem.
In Spain things are different. So far as I understand it, it is acceptable to walk where you want. However I advise strongly against wandering anywhere where fighting bulls are roving free. I've seen them and, despite years of road running and many hours spent in the gym, I think they will inevitable have the upper edge should it comes to a stand off.
I assume hunters have a right to rove where they will because they are part of a syndicate. And pay for the privilege.
Walkers are probably something of a novelty for most land owners away from popular tourist areas.
I am currently house sitting near Valencia and have two dogs to look after. They are both (now) very fit and need a lot of walking. Because there are not a lot of footpaths near to the house and the dogs are hopeless on the roads we frequently cut across some private land to get from one track to another. Everyday I expect the landowner to ask what we are doing. My only defence will be that the dogs are not safe on the roads. My limited Spanish is good enough to explain this but I hope it will never come to that. The area we walk through is overgrown agricultural land. No longer worked and littered with spent shotgun cartridges. At one time it was probably full of people. I like to think the owners will appreciate any paths being kept open.
I suspect that it is an English thing to be worried about walking. I always feel uneasy, wether in England or here in Spain, unless I"m in the high mountains or on a footpath. I think we just have to be brave and ready to accept, at worst, someone asking us to bugger off. If a

says Camino Particular then I wouldn't go beyond it. To me this means Private Property. Where I can I stick to footpaths or tracks. It's usually easier underfoot anyway.
What's the worse that's going to happen if you walk down a track? An irate landowner ranting and raving. Just apologise and go back. Of course if he or she has a gun then that is threatening behaviour with a firearm. Something very different in English law. But we aren't in England.
If only there were decent Spanish maps that had some bearing on reality.
Andy
ps Here in Valencia there are a lot of signs that suggest that the collection of wild mushrooms is prohibited. Not sure about asparagus though...