I did the same trip you envision last year at the same time, with a pretrip to Onion Valley. My trip report, which includes the food we ate, is
here, pictures included. Now, to get to your questions.
a) Onion Valley vs. Portal: We're spending 2 nights camping to acclimate. Is it worth staying at Onion Valley at 9200 vs Portal at 8300 or so. Will the extra 900 feet make a difference? Are there other advantages to staying at Portal?
No contest, the extra feet,and extra peace and solitude, are worth it. You will sleep better because you won't be hearing people all night long scaring away bears, packing up, blah blah blah (though Onion Valley does have some bears) And you can do some great acclimatizing hikes at Onion Valley (Kearsarge Pass!). When I did Whitney as a first timer last year, it was 2 nights at Onion Valley for me, no regrets. You do have another choice, though -- Horseshoe Meadows -- which is nearer to the Portal and to Lone Pine.
b) Outpost vs. Trail: Current plan is to camp at Outpost and try to Summit the next day, and make it back to camp at Outpost again. Is it worth it to try to make trail? I'm concerned I won't feel like eating and get a headache camping at 12,000 feet.
Tough one. I've done Trail Camp on both my overnighters to the summit, no regrets (I camped at Outpost Camp once with my dog, also, when I had no intention of summiting). But Outpost Camp is prettier and you'll sleep better (although Outpost Camp gets noisy at 3 to 4 am as people start hiking through). How much weight are you carrying? What I would do is see how you feel when you get to Outpost Camp. If you feel good, go for Trail Camp. Getting to Trail Camp will increase your chances of a successful summit, sleep or no sleep, in my opinion (others may differ), because overnighting at 12,000 will help you with the summit push, and instead of facing a sudden 4,500 feet jump in elevation, you will be looking at only 2,500. But be warned: some folks think the section between Outpost Camp and Trail Camp is exhausting with a backpack. If you backpack is much over 25 lbs ... well, depending on your fitness, might not be fun.
c) Water from Trail to Summit: I've got a prescription for Diamox and read you need more water. Will 3 L be enough? I weigh 110 lbs.
I am a female who weighs a little more than you, and I take Diamox (very low dose, now only 62.5mg once a day before sleeping at altitude), and 3 liters is fine for me for that part. Your experience may differ. If this is your first time using Diamox, try it at sea level first for a few days long before your trip (like, right now) to see how it affects you. At my low dose, I haven't really experienced that much increased diuretic effect, to be honest; I often experience that effect at altitude with or without Diamox, and I think that is normal.
d) Pack weight: I've read that you should not carry more than 25% of body weight. Is is true that men can carry more? I'm trying to tell my husband that. He's almost there.
Yes, but there is a question how much you have each been training with. You really should keep your pack to 25 lbs if you can (it is doable). Especially if you are not going to train with a similar weight pack ahead of time. We had an athlete, experienced hiker, in our group of 3 who did not heed this advice last year; she crashed at Outpost Camp, and my friend and I each had to take some of her weight so that the three of us could get to Trail Camp.
e) Food: Any good suggestions on food? My husband doesn't really like freeze dried. But he doesn't want to do dishes. Are there easy non-freeze dried foods (besides PB&J). I pretty much lose my appetite for anything except chocolate and nuts, but altitude does not affect him. We've tried several, including Mary Jane's and Mountain House and wonder if there's something else.
Tortillas, packages of tuna fish or chicken, Ramen Noodles, cheese, salami. But for dinner, I would go with freeze dried dinners, because you need as close to a real meal as possible to get the calories to get you up the mountain. There are alternatives to what you see at REI. Check out
http://www.trailcooking.com/. You can learn how to cook in a ziploc bag there (no dishes, just eat out of the bag!)
f) Weather: I was wondering how cold it gets at night? I was planning on bringing at 40 degree bag and a Pantagonia down sweater and gloves but looking at pictures, it doesn't look that cold. We have a tent. I'm wondering if I can ditch the down sweater and just bring a fleece vest.
You can get a relatively precise forecast
here for Trail Camp, (slighty higher altitude, so slightly colder than what you would experience at Trail Camp.
Me, I would totally bring the down sweater. You can always use it as a pillow. All three of us wore our down last year over labor day weeekend at Trail Camp. And don't forget wind/rain protection that goes over it.
Last year, Labor Day weekend, I was barely warm enough in a 25 degree bag at Trail Camp, and that was with a silk liner. A friend was toasty in her 10 degree bag.
Have a great time!
