Fong said:
Listening for the tonal center is not something I think I can do realistically.
Sure, you can hear the tonal centre, Fong. Not in all music, as some music is tonally very vague, but in most tonal music the tonal centre (or key note/chord) stands out as being the one that sound most stable and final. That's why most songs end with it. They sound unfinished if you end on anything else.
Almost everyone, (even young children with no musical training), can hear the tonal centre, unconsciously. Tonal music wouldn't make much sense if we couldn't.
Hearing it consciously just means recognising its quality and identifying it.
If you were to switch on the radio in the middle of a twelve bar blues, you would quickly recognise that it's a 12 bar blues and would know when the chord is changing to I, IV V, etc. That's only possible because you can feel when the music is moving to or from the tonal centre, i.e. the I chord. If you don't have an instrument handy (or perfect pitch) you can't know what the actual key is but you can tell when it's on the I chord by recognising it's 'home again' quality.
As you know many 12 bar blues sequences end the sequence on the V7 turnaround chord. When that happens we (musicians and non-musicians) can feel a strong urge to get back to the I chord to hear the sequence again. But if it went somewhere else instead of back to the I chord, we would either be disappointed or pleasantly surprised, either way we would definitely know something's up.
So you can definitely hear the tonal centre, and by listening out for it you can improve your ability to recognise it and then identify it on the guitar.