So about 1/2 mile after the first right hand turn you go down a quick descent where you'll easily pick up 40mph. Then, on the other side of the ravine is a hill, which while not really more than a quick power climb, you won't be doing anywhere near the 40+ mph when you crest it (more like 17-22). What invariably happens is you get a field with 100 people in it, they all fly down the hill, then compact at the very bottom before the climb out. Being only 5 minutes into the race, everyone's still pumped with adrenaline, acting stupid, etc, and there's not much room to maneuver.
The first year I did this race, YMCA and I were both on the back of the field during the descent chatting with each other when the inevitable pile-up ensued. I actually finished, because I refused to drop out, but was so far behind that it wasn't even funny. (and I think we were chatting about a crash that happened at that hill several years ago, ironically enough)
Last year I saw a guy go flying over the guard-rail at the bottom because he was squeezed off the road, and then about a minute after that someone behind me got squeezed out to the left, hooked my bars, and took me across the road on a zig-zag, that's when I abandoned.
I've seen pro's (Phil Gaiman) get crashed out in 5 minutes into that race on that course.
I also had a mechanical one year, where my rear derailer exploded.
I really don't think San Ann likes me very much...
The two years I did well, I raced 35+ with a smaller field, and I made sure to stay at the front on the first descent so I wouldn't be involved in the carnage. I'm pretty sure YMCA won the 45+ race last year.
My suggestion is to stay near the front, or at the very back and be willing to chase back on, for the first few miles.