The recently changed the website to make this the main directions from Rt.50, but it hasn't caused traffic issues yet. They used to tell you to get onto Rt.3 from 50, then go east on 450 for 6.5 miles before turning onto Crownsville Rd. It's probably 450 you're thinking of, since it backs up for miles if you don't get there early enough. And it's mostly due to the traffic light at Crownsville Rd, rather than the faire entrance. Coming across 450, from South Haven, you usually only have to sit through the red light once, and then straight to the faire parking lot without stopping.
This season I saw the first exception to this that I've noticed. I often get to the faire around 11 or 11:30, and usually can zip right in. But this past week was so ridiculously crowded that I saw crownsville road itself back up on this side. (The north side is a different story, as Crownsville Rd will back up all the way back out onto 97 and 32 sometimes).
The weather is probably going to be pretty good this weekend, so I'd expect a good crowd. But this past week was also Octoberfest (or "drunktoberfest" as we often call it), which is always packed if the weather is at all decent..