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There is a park with trails about 3 miles from the hotel called Tecolote Natural Park . A nature walk Sunday Mar 7th at 9:00 AM leaves from the Tecolote Nature Center. More Info here. This could be a possibility for people attending afternoon seminars. The Mission Trails Park, eight miles northeast of downtown San Diego is one of the largest urban parks in the United States. Many other possibilities are described on the city's parks and recreation site.
Kayaking
Aqua Adventures is located less then six miles from the hotel. They rent Kayaks for as low as $15 for one hour. You can contact Aqua Adventures at (800) 269-7792 or at their website below.