I had Spectrum up until about a month ago (had been with them since Time Warner days). Based on my experience and what I've heard from many others, the only real deals to be had are if you're in an area where there is legit competition from another broadband provider (typically fiber). Can't hurt to call them up and mention whatever deal(s) you're seeing from a competing provider, but I've read from several sources that they maintain a fairly accurate database of who the competition is and what speeds/prices they're offering down to the neighborhood level.
Personal observation... ATT Fiber was installed in my neighborhood recently, and the mailers, text messages, and emails for previously unheard-of rates from Spectrum started up within weeks.