OK, more digging and I found that this resolved the broken pipe issue when num_workers>0:

num_workers = 4
batch_size = 32

if __name__ == '__main__':
    trainLoader = torch.utils.data.DataLoader(traindata, batch_size=batch_size, 
                                              num_workers=num_workers, drop_last=True)
    valLoader = torch.utils.data.DataLoader(valdata, batch_size=batch_size, 
                                            num_workers=num_workers, drop_last=True)
    testLoader = torch.utils.data.DataLoader(testdata, batch_size=batch_size,
                                             num_workers=num_workers, drop_last=True)

Thanks so much for the help with this!  If you have any comments / suggestions on the class I modified from one of your posts please let me know!