I worked every other week of last year in central Mexico. Only got sick once and I'm not blaming it on the water or food, could have just been happenstance. I never drank 'tap' water so to speak, only bottled water. I did use ice in my drinks though. I only did that in fairly 'nice' places. My coworkers swore that you need to keep your system lubricated with Tequila to ward off bacteria. They didn't get sick either. I don't drink, so not sure if thats true or not...
Went to Cozumel for a wedding a month ago. At the resort I used the ice in my drinks with no issues.
As to tipping, we didn't tip every Tom, Dick and Harry, but did some. Resort said it was included in their workers pay.
