Lambecc,

I live in Studio City, and get bad AMS (yearly!), so I know your pain.

Although you don't mention urination, the volume of water you are discussing should be sufficient, and I wouldn't adjust that particularly. You might consider some sort of electrolyte addition, although the literature is mixed on that. I personally prefer to use 1/2 strength "whatever" you might choose. I drink more when it is flavored.

Diamox is definitely something to look towards. A small dose, (1/2 of a 125 mg tab) taken at bedtime, starting 2 days before going to altitude, is what I usually prescribe. If you've never taken it before, I recommend using it at home once, just to make sure you won't have a very unusual reaction that messes up your trip.

The diarrhea is an enigma. It does not technically fit the Lake Louise criteria:

http://www.high-altitude-medicine.com/AMS-LakeLouise.html

Which is restricted to N & V, or anorexia. However, it is part of the same system, and the criteria were developed in 1991, and there are clearly some things that are recognized as being altitude related outside of the criteria. Personally, I'd treat is as altitude related, and you lose nothing by doing so.