Where are some of the best, fun places to hike near San Diego? I'm not looking for anything too long or too hard; looking for an easy to moderate hike that is about 3-5 miles long? Anything shady by the ocean?
Not much by the ocean that is shady -- San Diego is not heavily forested. Here's my list:
Balboa Park (especially the Zoo which is more of a botanical enclave than an animal one)
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Ocean Beach Walk begins at the south end of Mission Beach and adjoins the sandy ocean beaches for miles. A walk to Pacific Beach Park at the Pacific Beach Pier is about 2.7 miles one-way. Along the way Ocean Beach Park changes its name to Ocean Blvd. While there isn't much shade on the beach, there will be numerous cafes, pubs and such that will provide hideaways from the sun. The walk could be extended north of Pacific Beach Park, too.
My favorite coastline hike is Torrey Pines State Park. You can start on the beach and hike up over the cliff. It's a sandy hike through the California coastline chaparral. I don't think you'll find anything shady near the beach, as the natural vegetation near the beach does not include tall trees. Bring a hat and a waterbottle (hands free), and wear sunscreen.
Torrey Pines State Park is by the ocean and has Torrey pine trees on Broken Hill Trail Razor Point Trail. If you combine trails you can hike for 3-5 miles. The easiest trail is Guy Fleming Trail which is forested with ocean vistas.