Non-Competes for Computer Repair Independent Contractors in CA

I've owned a computer repair business for about 6 years now. I'm about to hire my first employees. I'm thinking of hiring 2 or 3 people as independent contractors. Compensation will be based upon the computer repair service they provide. My concern is that I'll bring someone on, train them how to repair computers, then have them leave and just advertise the service alone on Yelp, Craigslist, the community, and undercut me on pricing because they won't have the overhead to operate out of a store. I researched non-competes in CA and from what I've read they basically can't be enforced here. Is there anything I can have new employees sign that would protect me? Thanks.