Hi everyone.
Where are you guys?
Don't worry about top less in a spanish beach. Now, more and more, it's normal to see ladies doing top less or wearing c-string in the beach. Even really young girls are doing top less now. Noboy'll be surprised for see two more bobs xD
And if you go a nudist beach, probably, you'll feel better naked than with clothes. When everybody are nude, it feel strange to wear clothes.
But remember that in fall, even though in october the weather is fine, the beachs have few people. So, it's possible you feel alone in the beach or with very few people aorund. Especially for monday to thursday.
In sunny days, we make good use of the beach to have sex

So don't care about thing like that.
Good trip and enjoy your vacances in spain.
Regards.
Note: Sorry for my english. I hope you understand me.