Gelsomina, first let me say that you're getting good advice, varied as it may be. I personally know and/or have hiked with many of the members who've posted on this thread. They're each and every one good, sincere people who (1) are giving you their honest perspective and (2) would always stop to assist a hiker in distress (wazzu's got a helluva story about her first attempt at Whitney). The key here is taking the advice that's right for you. I believe your post has generated more than the typical response for a first-timer's questions because you've been utterly honest about your experience level and are genuinely seeking advice, and it's evident you have a well-thought-out plan. Many first-timers don't, nor do they listen to advice from people who have been in their shoes if it runs counter to their mindset.
Unless you have absolute certainty in your partner's dedication to you, treat this mentally as a solo hike. If that creates anxiety, the upside is there's really no such thing as a solo hike on Whitney in summer due to the crowds. The downside is that you have to mentally and emotionally be prepared to mostly do it on your own. As I said before, if you stick with that training plan you'll have the legs to climb Whitney. That leaves altitude sickness and injury as your most likely potential issues. There will be virtually no snow or ice on the mountain come August - the primary cause of most injuries - so you really need to focus on beating the potential of AMS, as you've not been above 10K' before (or I assumed so from your initial post, which is the reason I suggested Diamox). AMS aside, all this hike is in August is a very long, very tiring walk on a well-defined trail. You're not climbing the Matterhorn, so don't psych yourself out before you begin (it happens).
Acclimation is the best deterrent to altitude sickness. Two nights at 10,000 feet (Horseshoe Meadows) is the recommended dose before tackling this mountain. Once your body is acclimated to sleeping at X altitude (at or above 10K'), the prevailing wisdom is you're good for another 2000 feet the following day. The problem for a dayhiker is that 4500 feet are waiting for you - hence the many flame-outs at Trail Camp (12,000 feet) or on the switchbacks above Trail Camp.
I was one of those AMS flame-outs my first time up Whitney, and I was solo. I had myself (erroneously) convinced that I was one of the lucky few to have no predisposition to AMS, so I didn't take much precaution. I had been above 14K' a number of times with no ill effects, and once even went from sea level to 14K' in less than 12 hours, problem-free. Why acclimate for Whitney? That's one of the nefarious things about AMS - it's unpredictable. Sherpas in the Himalaya who've been running up and down 8000-meter peaks their entire lives have been known to die of altitude-induced edema at 6000 meters or so.
Anyway, trust me when I tell you that making my way down from 13,500 feet on Whitney with raging AMS, by myself, was the hardest thing I've ever had to will myself to do. Worst headache ever, incessant nausea, kaliedoscope dizziness, DT-shakiness - but the worst symptom to overcome was the most incredibly lethargic feeling. I just wanted to lay down and go to sleep - screw everything else. Of course, I'm a guy, so I lied every time someone would ask me if I was OK or needed assistance. Gotta perpetuate the rugged, independent male stereotype, right? Actually, I just couldn't believe I had AMS and was mentally trying to write it off to food poisoning or some other malady outside my control.
Needless to say, proper acclimation became Job One every trip to altitude after that. I never, ever want to feel that way again. I've had no problems since, and have only used Diamox on one occasion, that being taking my wife and 11 YO daughter up Whitney last year for their first time (I was taking no chances with my girls, so we were a Diamox piss-happy family that trip). Diamox isn't a magic bullet - you can still develop AMS with it in your system - but it helps aid the acclimation process and can often provide that extra oomph many people need to ambulate reasonably well above 12K'.
White is relatively easy on the legs compared to Whitney, so if you go that route it should tell you whether Diamox is in your future. Just be sure to do the other things properly - acclimate, hydrate, eat and pace - and you'll reduce the chances of AMS to an absolute minimum. If you have an inkling you might be on your own on the mountain at some point, these are your priorities. Diamox is an option, but often the right one for many people. My wife historically couldn't go above 12K' without some serious AMS setting in, regardless of acclimation, but Diamox has given her that edge she needed.
Best of luck and be sure to let us know how it goes!
