Most all of the books on how to improve memory suggest to say what you want to remember aloud, again and again.
I like Skinnerian Behaviourism in learning things, and I take "thinking in words" as silent, to subliminal, verbal behaviour. Social conventions often dictate "silence", but the rules have plenty of exceptions, mainly with things socially popular (i.e., when I was the unpopular student, any whisper from me in the library was prohibited, but about any of my concerns with my studies being disrupted by Mr. and Ms. Congeniality having a gabfest, I was told I lacked concentration and was just too easily distracted from reading in the library). The physical movements of typing words can also be used to "verbally think" with your fingers. Many memory tricks rely all kinds of modalities of every basic sense.
Neurological impairments in my speech also makes it difficult for me to initiate speech (at times, I have write the word "Hello" down on paper, then read it off aloud to start my speech, other times, epileptic seizures cause me to "speak in tongues" or to be unable to speak at all, and then, my speech tends to drag on (most like a side-effect of the "Geschwind Syndrome"). To accommodate many of my impairments, I regularly read off the time and my GPS location with audio/video recorders as I'm traveling (mainly walking) in public. Some individuals (and officials) have raised issues over my accommodations, but with a repetition of starting "adminitrative remedies for reasonable accommodation under the ADA" phrases, they usually back off. During my epileptic seizures, my time, place, and activities are recorded, and the remarks and behaviours of other people and officials are often much more bizarre than mine from my seizures (some witnesses/officials have very bad memories also, either that, or they are prone to tell big fibs of what they said and did). Whether the ADA offers me any real protection from the State not allowing public records might end up in court someday.
Most everybody talks to themselves (even if they deny it), it's just if it's "appropriate" (like wearing the "correct" campaign button at a campaign meeting). Then, as many cell phone users illustrate, the public will have to tolerate it or go "un-ADA protected" private themselves (where wheelchairs, guide-dogs, etc., can all be prohibited).
Tadzio