generally we have pretty much all year round sunshine. However late october to early april is most likely to have rain, as regards when and how long is a bit trick last four years november has been different, one really wet, one really warm. But generall 20c + in the daytime and cool in the evenings. Alot of the afternoons get cloudy at around 3 or 4 pm. Try
http://www.wunderground.com for a history (airport code LPA , change the location to maspalomas as Las Palmas can be ALOT cooler than the south coast) But generally speaking we have maybe 2/3 bad weeks a year which is better than most places