Cycling in Andalucia

I cycled from Portugal to Valencia 3 or 4 years ago and had no problem without helmet.it was in May with excellent weather.Sierra Nevada is wonderful!
I met last month ,in Myanmar, a spanish cyclist from Granada who is cycling everyday day without helmet around Granada! he was not even sure if it was compulsary!!!!
Spain is a Latin country ! so wear your helmet if you want and don't wear it if you don't want!

Officially you can't cycle over the Muhacén road, which is the 3000m one, and if you meet a guardaparque on the way up you will be prevented. Of course, if you meet him on the way down its too late for him to stop you. Unofficially, you are unlikely to be able to get over it in April unless you carry the bike strapped to a rucksack, (which might be a way of getting past the official at other times). I had friends you tried in May and failed (in the days before Guardaparques saying no), though that's going back 20 years and these days I think you have a better change in May, in a practical sense.

You are unlikely to have snow problems on any other road in southern Spain in April. They have weather: a friend of mine always seems to find it cold and wet when she goes there at that time of year. But it is more likely to be pleasantly warm.

I've biked in Spain twice and commuted by bike a third time. When one considers that no one in Spain even bikes (except the racers), and Barcelona is just about the only city where you'll find cyclists recognized by the city (ie. bike lanes), one realizes that this law scares more people than not. Spain is a wonderful country to bike in and I have always found the sheriffs to be very friendly. Don't think you'll have a problem.