Hi, I wanted to reply to this myself because he asked if anyone had ever gotten it while their partner was on Valtrex. HAND RAISED 
I was told by my partner that she had HSV2 before we slept together. Before we were married, we used condoms (this was before I knew more about the disease and found out that even condoms are not a guarantee of safety). After we were married, we stopped using condoms (we hated them LOL), and she was taking Valtrex and I figured, "What the heck, we are going to be together for the rest of our lives so even if I got it, no biggie."
Six years later, she left me. To that point (mid-2008), I still had no outbreaks. In the fall, I went and got tested and as you would expect from the start of this post, I was HSV2+ (this was the specialized HSV2-specific Western Blot test). I was also HSV1- and thankfully HIV- (not that I ever expected I would be HIV+ as she was also negative).
I did not have ANY outbreaks until about 1 month ago. Then, out of the blue (and having had no other sexual partners since my break-up) I got an outbreak. It was fortunately not very severe (went away in about 5 days and didn't hurt terribly badly - she had told me her outbreaks were REALLY REALLY awful so I was prepared for the worst). I have had a follow-up mini-outbreak about 2 weeks ago, for just a few days.
I have no idea whether I will get any more or not. My only two outbreaks came at a time when I was very stressed over other things so I imagine that might have helped to bring it on. I also had no meds (my doctor had refused to prescribe any Valtrex or Acyclovir because I hadn't had any outbreaks, LOL). Now I have a prescription, but I am not taking it for suppression, because honestly it just doesn't seem all that big a deal for me. I will take the ACV if and when I start to feel an outbreak coming on and see what happens. Beyond that, I will just live with it.
So YES, you CAN get it while your partner is on Valtrex (and to confirm at NO time in our marriage did she have any VISIBLE outbreaks although as has been pointed out, you can have very small outbreaks that you can't even see, and of course, you can shed virally without knowing it at all).
The other thing to realize (which I only found out recently) is that it is NOT about having contact over and over again. You only need ONE CONTACT to contract the virus. Like any "numbers game" this is just a crap shoot. The odds are low in any single contact that you will get it, just like the odds of the roulette wheel coming up 17 are only 1 out of 38. But if 17 comes up the FIRST time, then that's all it takes. Valtrex/ACV and condoms essentially INCREASE the number of numbers on the wheel (i.e., the reduce the odds of hitting that "one time"), but any given person can do it ONCE and get it, even with Valtrex and condoms, and another person could do it over and over for years and NEVER get it, simply because the odds are long and you never know when your number will come up.
The difference between theory and reality is that in theory,
there is no difference between theory and reality,
but in reality, there is.