Because it's a little warmer, most people stick to the coast in the southern area of Spain. And that's totally logical. But boy, we sure do enjoy the interior more. We find the coast very busy and industrial, and really not that scenic. And if you want free motorhome parking, it's not that easy to come by, and you likely won't be alone.
Yes, there are also a lot of campgrounds along the coast. But they're not cheap, and we remember from past experience when we were here doing a motorhome exchange in 2017 that they can be very crowded, with not much space between sites.