Mount Laguna recreation area is a great place to visit the snow! There are tons of great trails in the area, including the Pacific Crest Trail. Keep in mind that if you are going to park anywhere in the area, you need to purchase a $5 Adventure Pass. There are places in Mount Laguna that you can purchase it from, so don't go without!
We chose to walk around Big Laguna Lake on the Big Laguna trail and then looping up on the Sunset trail. Both trails are well marked, although the trail got a bit lost at the south end of the lake. I think the winter water had swelled the lake over the usual boundary as one of the trail signs (of which there are many!) was in the water.
The trail was a bit muddy and definitely snowy, but easily navigable. Get a map before you head out, or use your smart phone/GPS to stay on track. There is a large network of trails, which is great for exploring, but make sure you don't get lost!
Along the way there were lots of cars parked along side the highway and kids sledding down the hills. This is a great place to spend a day with the snow! Make snow men, hike, mountain bike, sled, or just have a snowball fight. Whatever you do, have fun!