The problem of mixing MF towels with regular laundry is you take the chance of mixing cotton fibers with your microfibers.
I always wash my microfiber towels by themselves using a microfiber detergent (Used for treating, cleaning and preparing microfibers because it is a powerful degreaser and strong detergent with the absence of bleach or fabric softeners, both of which mean a certain slow death to microfibers) - every other cycle I'll add vinegar to the rinse to maintain help softness. Always dry on low heat for no more than 15-20 minutes. Drying on high heat will destroy the microfiber towels and they will lost their softness...