Regarding your questions, your first question was:
Should a devotee always speak the truth to everyone
in all circumstances?
The answer is yes.
One Should always speak the truth. But a qualified devotee will be able to speak the truth very palatably to everyone
so that it will sound pleasing even to his enemy. That
is the art of speaking the truth. We must speak the
truth to all people, but how you say it is another thing,
satyaà bruyät, priyaà bruyät. When you become
a little more experienced in Krishna consciousness
by preaching, and if you are sincere and serious to
make progress in spiritual understanding, you need
not have to worry yourself further, because the truth
will always be spoken by you in the proper manner.
Krishna will give you that intelligence; you need not
be concerned for it. Simply try to please him always
by your sincere service and chanting. That’s all.
Of course, for doing business with businessmen
you have to lie. Just like Krishna himself, the
Supreme Personality of Godhead, sometimes he
also had to also fabricate something in emergency
situations. Although he promised not to interfere
in the battle of Kurukshetra, he was forced to
break his promise just to save his pure devotee. So
there is no prohibition that one shall never tell a lie,
because for business of carrying our propaganda
work sometimes it may be necessary to lie.
Krishna consciousness means practical living, not something
utopian or idealistic and vague. We simply do the
needful, whatever pleases Krishna most. That’s all.
Gradually you will understand what it means
to please Krishna and what it means to displease
Krishna. That you will learn by studying our books
and by yourself engaging in practical devotional
service. In material dealings there is always
something undesirable, but even so, you cannot
give up your occupation. Just like fire is very pure,
but still there is some smoke. You cannot avoid it.
All these things can be rectified when the result is
offered to Krishna. Otherwise, even though you may
do very honest business, it has no utility whatsoever.