We went to Idyllwild for our 5th Anniversary in August - a cute mountain town with lots of good hiking. It cemented my choice of manzanita as my favorite tree! Restaurants: Gastrognome - yummy asparagus and portobello penne in creme sauce, Nature's Wisdom - ok sandwiches, La Casita - good veggie burritos and veggie tamales, Mile High Cafe - a little out of town, yummy veggie burger and nice salads and great art.
note: a decent number of highly rated restaurants were closed, e.g. Swiss Fondue
Fun place to hang out: Idyll Awhile Wine Bar - they have music on the weekend evenings, and a tasting option which was fun!
Hiking: We did Suicide Rock (~7 miles, on the upper end of difficult just below strenuous) and Ernie Maxwell (~5 miles, moderate). Nice views of the forested vista and mountain peaks, plus both had a decent amount of distance under the canopy of trees so we didn't get too hot. Gorgeous groves of manzanitas.
Walking around town: they have painted deer around town - fun to check out!