Well, since no one is posting

I shall share what I have learned in case anyone else needs help. In California, by law, the minimum premium for liability insurance is $695 (per year) so anyone else who gives you a quote less than that isn't aware of CA law and your actual premium will be at least $695. Markel has been the most helpful so far, and I have called at least 10 different companies. Equisure was pretty nice to work with too, but Markel was more informative. Guided trail rides are the riskiest equine endeavors a horseman can participate in as far as insurance companies are concerned, and thus insurance premiums
start at $3000. If trail riding is part of your instruction, however, it is not considered a 'guided trail ride', like me, I take my students out on trail as a reward and a chance to talk about lengthy topics. Also, I can only have up to two horses and riders per instructor. Any more than that and the insurance cost doubles. I've got my own personal thread going here, but I hope it helps someone else. :)