From DGF:
Sorry I am not an expert on the best fabrics to wear in the heat.  I would suggest that dress (based upon the situation) like you would in Minnesota during the hottest parts of July - current humidity right now is 80% 

 and the temp forecast for my area this week ranges from a low of 70 to a high of 91.  
Also not sure what they mean my "no shorts of any kind" - do they mean outside the work setting?  Maybe your area is more heavily populated with Muslims, but otherwise where I live (and in Manila and most the of country) it's perfectly acceptable to wear shorts while shopping, going out to eat, etc.  
Same thing for suits - women wear normal swimwear at the beach as they would in the U.S. Maybe a few less bikinis?  But I'm not even sure it's that different.  
I have no idea what a rash guard is, but by the sound of it I don't know why it would be necessary.  Maybe they mean a swim shirt?  Again that might be a good thing depending upon your complexion - we're close to the equator.  But as a necessity due to customs?  I don't see it.