Thanks for the responses. I feel better about our dates. Now I have to convince my friends about the trip. Still don't know how I want to do the trip, I have to resist the temptation to move around and see/dive too many places.
On the weather topic, I also emailed the Atlantis Resorts and got this response:
There is no real bad time to visit the Philippines, both air and water temperatures are great all year round, so is the diving. We will get an occasional shower during July and August, but it is tropical, so usually blows over in half an hour or so.
In Dumaguete we have excellent weather most of the year with a minimal risk of typhoons during the last six months of the year. In fact Dumaguete can almost boast its own weather system; surrounded by mountains much of the bad weather associated with typhoons or the rainy seasons in other parts of the country is deflected away from the area.
And I found this on the El Galleon resort website:
We are an all year round dive resort with the sea normally moderate during December to March and calm during April and May, often talked about by the travellers (not divers) as being the best time of year to be here. Water temperature during December to mid or late February 23° to 27°c.
From June to November (typhoon season July to August) can be and often is some of our best diving conditions. We do get rain (sometimes) during these months, however its normally at night either early evening or early morning leaving the days to be fine and mostly sunny with sea condition being excellent. The visibility is often at its best during this part of the year, however its not called typhoon season for nothing. There is always the risk of having a typhoon pass by and leaving behind it a day or two of rain and coursing some swells. Its rare that a typhoon would pass through Puerto Galera and in the past years we had one in 1996 and the next two where 2006, May and December! None since then as of this righting that have affected Puerto Galera. Weather temperatures, mid to late February to November 28°c to 30°c