Based on recent trends, I'd say it's too early. I'd recommend keeping your eyes open starting maybe 3 weeks before the 1st preview - though it could be even later than that.
I expect the code will be something along the lines of "3U3" or "DRIVE3U3" or "3U3DRIVE" or something like that.
Also, I wouldn't be too concerned about missing out. I don't think 30U35 tickets sell out very often - maybe for individual performances, but if you're flexible with dates it's usually pretty easy to get in. I expect How I Learned to Drive will be more popular than some of their other recent shows, but historically I've found that even the more star-studded productions haven't posed much of a challenge.