Agree with leaving at 4:30pm approx. After 5pm it's the rush hour and traffic becomes much heavier. The AR lounge (Salón Cóndor) is not outstanding but it's probably better to read a book there instead of being stuck at the highway.

Immigration at Terminal C shouldn't be an issue since there are not many flights leaving close to DL's - AF, AZ and KL have all left and AR widebodies only take off after 11pm.