My parents went a while back, under the auspices of the People-to-People program, a fairly high-end NGO that sets up cultural exchange program for professional groups.

First piece of advice: trade in your luggage for lightest stuff you can find; expect to have to carry it.
2) Don't drink water that did not come with a seal on it; don't trust the 'boiled water' in the hotel.
3) Take imodium, and consider getting your doctor to give you a Rx for a stout enteric antibiotic

My father had health issues. His doctor put together the equivalent of an Advernture Medical "Savy Traveller" kit. No problemm with the authorities, at least on that trip.