I was just there and did a couple runs. We stayed off site so not exactly the same starting location, but I liked making a big loop around the park which is basically what was suggested above. We stayed off of Walnut, so I ran down Walnut to Katella to Harbor to Ball and back to Walnut. It was about 3.5 miles. I didn't go as early as usual so there was a bit of a crowd on the sidewalks at the entrance to the park, but if you go early enough that won't be an issue! They're busy roads but there are sidewalks all the way around, even over the expressways. I felt a little safer being in a busier area since I was unfamiliar with it. I also ran through some of the neighborhoods around Laster and Katella, but I had to keep an eye on the map a little more there.