I went to Madrid about 3 years ago.
Despite the size of the city, none of the people renting themseves out were particularly hot.
I even went to the rent boy sauna and if I were forced at gun point to take someone, the best candidate was a customer even older than me. The best working lad there had an enormous chest, matched only by an even larger gut. He was probably over 40.

There was a rent boy bar, but they didn't even open until after midnight, so I didn't bother.

I can't imagine The Canaries are much better for boys ? Same country, less scale.
I see the attraction if you just want a week away from the British winter.