Are there any natural ways to beat traveler's diarrhea?

Yes. Simple avoidance measures help: wash your hands, drink bottled water, avoid ice and eat cooked food served hot. Mild traveler's diarrhea (td) can be 'treated' by staying hydrated. Use special rehydration beverages if dehydration is a concern. Most td will go away on it's own. If you have fever, blood, or dehydration contact a doctor.
Yes. Avoid any unsure water source. Any drink (coffee and tea included) that doesn't come in a bottle should be considered unsafe. Swimming in unchlorinated fresh water is also unsafe.