Can people without symptoms spread mono?

Yes, sort of: After getting mono, due to ebv virus, a person will have ebv virus in his saliva sometimes. If he does heavy kissing with people who did not get ebv as a child, then those people can catch ebv from him and get mono. However, if he raises his kids in a way where they share foods, drinks, spoons, straws, normal kisses, etc..., his young kids can get ebv from him and have only mild symptoms, not mono.