When I cook quince that can be very tannic, the astringency is removed.
This occurs even without lengthy boiling.
Try cooking or baking a couple of the pears.
I have never perceived bitterness in quince, some people are more susceptible to bitter sensations, if that is your problem with the pears.
Pupmom,
I guess that I'd have to ask the same question: "Are you sure that they are Bartlett pears?" Was your pear from a reliable source that could be trusted to provide "the real thing?", or was it already on your property and you were told that it was a "Bartlett"?
I also agree with Chris M. that those pears sound like they'd be ideal for use in natural fermentation to make a traditional Perry (i.e., the pear equivalent of a traditional fermented apple cider).
If the pears are unpalatable, and you have no interest in naturally fermented fruit beverages, you could just put them in a compost bin and replace the tree with an accurately labeled pear tree from a reliable source. So sorry to hear about your disappointment when you got fruits! Inaccurate identifications can be a tremendous frustration! I've had a couple of apples like that after the patience of growing them to maturity.
Take heart, and start again. 
Best wishes,
Reinettes.
Idyllwild
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Marsha H
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