The first thing you have to do is find out if you are regulated by the LA Rent Stabilization Ordinance.

If you are, then READ IT to find out if an occupancy limit is prohibited or not.

If you aren't regulated by the RSO, then I don't imagine that an occupancy limit would be prohibited as long as you aren't discriminating against families with children (which you apparently aren't) and have that specified in your rental contract and your advertising so that prospective tenants are aware of the limit up front.