People will drop; even if they don't, just talk to the professors and I'm sure they'll let you in if theres a cap. I don't know about conflicts with other econ classes, but you can look that up online or deal with it when it comes up (check Spring 2008 Evening Prelim Exam Schedule
. Actually, now that I think about it, the prelims were in class so as long as you don't schedule conflicts into your schedule you'll be fine. The most this class has to do with engineering is CS (so no, not really); in fact, I'd say that at least 1/4 of the students were CS majors (myself included).