Each tour requires about 2 miles of walking and lasts approximately 2 hours. Both tours are available every day of the week, except some holidays (check their website). Tours start at 10:00am and 3:30pm. If you do both tours you will get a really great feel for Downtown LA.
PLEASE note that although the tours are free, you should ALWAYS donate a minimum tip/contribution of $10 per person. This allows these great folks to continue to provide such a great service. Trust us, even with this small tip, these tours are an amazing bargain.