charts test scores and excellent grades, etc. So do many who go to school at BYU. I actually had a classmate in high school who had a 4.0 GPA, got a 1600 SAT, grew up a University of Utah fan and was set on going to an Ivy League school. He ended up doing Computer Science at BYU.
I can completely understand why someone would want to go to the best school that they can, and BYU isn't going to be at the same level as MIT, Stanford, Georgia Tech, etc., but going to BYU is in no way underachieving.
Also, when looking at BYU's #102 ranking in Engineering, that's their Graduate School ranking (i.e. for a Master's or PhD). It really has very little bearing on their undergraduate ranking - especially since BYU is known to put more emphasis on undergrad education as opposed to graduate education and research compared to other universities.
For reference, their undergrad ranking for BYU is #96. To me, that ranking is high enough to not be a hinderance to getting into a top grad school, and the price is a bargain compared to other schools. Obviously if you are debating a top 10 program vs. BYU that's a different debate, but there isn't going to be much of a difference between going to a #60 ranking and a #96 ranking.