Don't flash what you don't want others to see and steal. - always my motto.
when people don't see, people don't know. simple.
Even if you need to carry a lot of cash with you, always flash LITTLE money when you need to pay for purchases/tickets etc.
it all boils down to common sense.
as for money in the hotel - some times, it is really luck that.
common sense wins 80% of the time.