There are a million places to run in Orange County - in Costa Mesa, a lot of people run over at the Talbert Nature Preserve and/or along the river bike trail. In fact, the river trail is so long, you can go on a lot of different runs without covering the exact same route - I think it runs all the way out to the edge of the county border by Corona - there's another big regional park in the area of Talbert, I think it's called Fairview Park.
Also, there is a great bike trail in Newport along the peninsula and you'll find people running there a lot - ditto for Huntington Beach [and there's a dog beach there, too!]. Going up the coast toward Long Beach, there's a wonderful area called Bolsa Chica Wetlands - there are tons of trails, mostly dirt but some paved, and I see lots of runners there, too.
Going to the south of you a bit, there's the Crystal Cove and Laguna Coast Wilderness Park areas - they both have hills so it can be a butt-kicker. You're also not too far from the UCI area and there are quite a few running trails around there.
Going inland slightly, there's Mile Square Park in Fountain Valley and tons of trails, parks and so forth in the Irvine area.
One of the things I really like about living in Orange County is that there are plenty of parks and trails everywhere - I'm not exactly a runner myself but my husband is and we both like to hike or walk - all of the bike trails are paved and open to people on foot, whether walking or running. I think OC has about 250 miles of bike trails so that should keep you busy for awhile. We also have several hundred miles of hiking trails in the county so when you run out of bike trails to run on, you can hit those and stay busy for awhile longer, haha!
If you want groups to run or hike with, check out Meetup.com - there are dozens of Meetup groups in our area. If you are a trail-runner, check out the Orange County Sierra Singles group - they have hikes [including trail runs] on weeknights in Irvine, Long Beach and other areas. The official meeting place of that group is in the rec center on Park, right next to Triangle Square off 19th & Harbor.
And by the way - welcome to Orange County - hope you enjoy your stay!
Sorry I am not in the Orange County Area. I wanted to say hi and welcome to Spark People where you will find lots of information and tons of support and encouragement from all our members. You will find that we also have fun along the way. Drink your 8-8oz glasses of water a day, watch your portion control and walk, dance or do any exercise you enjoy. Use your fitness and nutrition tracker daily. These tips will definitely help in lowering your numbers. Don't expect miracles right away...this is a lifestyle change not a diet. You will be much healthier in the long run. Post any concerns, comments or questions you may have and someone will respond quickly. Start each day with a positive thought just for that day. Reading and reflecting on an inspirational thought or message before you start your day can put you in a positive frame of mind. Your thoughts determine whether you have a good day or a bad day. Fill your mind with positive ideas, suggestions, and thoughts. You will find it will change your attitude and changing your attitude can change your life. Sometimes just reading an inspirational quote or a short paragraph helps one see the positive in a situation. Sometimes as your day progresses you just need to take a break…Take a mental break and read or think about a message of inspiration. Never underestimate your power to change and improve! You are a good person, with wonderful qualities, and you can reach your goals! If I can be of any help to you, please let me know with a spark mail or a comment on my page. I am here for you. God bless you on your journey to a healthier you. Hugs, Helen