If you're coming from LAX, it will take you approximately one hour by car to reach Walnut. If you prefer public transportation, there are daily train and bus services that run from downtown LA to Walnut. Keep in mind that you'll need to rent a car or take a taxi to reach the individual locations listed in the itinerary.
If you have more time, you can explore nearby attractions such as Sycamore Canyon Park and Thoroughbred Racing Club. If you have less time, you can spend half a day at the California Botanic Garden and take a shorter walk at Mount Baldy. Additionally, you can hire a local guide to show you around the area to maximize your experience.