Timetable here:
https://easyupload.io/puwg66
(Ignore the big green 'Free Download' box. Scroll down to the one word 'Download' and click on it to download the file to your computer).
It's 'Línea 15' that you want from that document. The map is on the first page, with the summer times on the second and third pages and the winter times on the fourth page. Note that there's no evening service in the summer, except on Saturdays, when there are buses running all through the night into Sunday morning.
[NB: I suggest using that document as a guide to the level of services that you might find only. I found it online but it's undated, so there might have been changes since it was published. Check times locally when you get there].