The Lavaderos de la Reina walk is a good option, if you want to go trekking in summer.
Lavaderos de la Reina is an area of lush meadows fed by mountain springs at 2500m, near Güejar Sierra Village. The best time to visit is in early summer, when the melting snow feeds the gushing streams. The first part of the route also gives some great views of the Sierra Nevada.
It is a 6 hours walk, but not particularly difficult, although there is a steady climb at the beginning, and you also need to clamber down some rocks beside the waterfall. There are no signs, but the route is relatively easy to follow.
The Lavaderos are at their most beautiful when the snow is melting around May/June, but it is possible to do the walk in summer and early autumn as well.